There are lots of supporting characters running around in this fandom: the Internet Movie Database cast lists for Curse of the Black Pearl (CotBP) and Dead Man's Chest (DMC) can help you keep Marty straight from Twigg and figure out which one is Pintel and which is Ragetti.
A few notes about names: Although we've since learned that Norrington's first name is James, there is some fic (usually stories written early in the fandom) that uses other first names for him. You're also likely to run across references to the unnamed officer (played by Greg Ellis) who says, "That's got to be the best pirate I've ever seen," in CotBP. His uniform indicates that he's a lieutenant, and, although it's not listed on IMDB, his canon last name appears to be Groves. In correspondence with fans, Ellis put his stamp of approval on the first name Theodore; this has no canon basis, however, this is the most commonly used name for him in fanfic (the same character has been called Bush by at least one writer, and Ellis is another commonly used first name for him). Lieutenant Gillette is often given the first name Andrew, although there's less consensus on this choice.
Portmanteau pairing names are often used in the Pirates fandom. The most popular is Sparrington, for Jack/Norrington slash (which is also called Jj). Others you might see include Willington (Will/Norrington), Gillington (Gillette/Norrington), Norribeth (Norrington/Elizabeth), and Jackstrap (Jack/Bootstrap). You may also hear someone talk about her or his OT3 - that's short for "One True Threesome" (a riff on OTP or One True Pairing), and is often used in reference to Jack/Will/Elizabeth stories.
The Official Website
First draft of the CotBP script
DMC shooting script
The Salacious Historian's Lair
Historical Resources for Fanfic Writers
Erin's Historical and Nautical Notes
There are even more historical and nautical resources listed in this post.
Live Journal Communities and Resources
Fandom Overview on crack_van
List of pairing specific essays on ship_manifesto
Discussion and News Communities
arrrrr: "A community for fans of Pirates of the Caribbean. . .Drooling, pics, fanfic, links, gossip, anything PotC goes." (This is primarily a news community, rather than a place to post fic.)
before_the_mast: "We are a Pirates of the Caribbean fandom newsletter for the minor characters of PotC."
cotbp_fandom: "This community is for fans of Pirates of the Caribbean: Curse of the Black Pearl, who are *not* fans of Pirates of the Caribbean: Dead Man's Chest."
despatches: "A somewhat regular newsletter for Age of Sail fandom happenings"
potc_discussion: "This is a community for discussion anything and everything about the three Pirates of the Caribbean films"
potc_pairings: "This community is open to any and all pairing discussions, icons, graphics, fic, you name it. . ."(low volume community, primarily fic postings right now)
isla_tortuga: "a Pirates of the Caribbean fandom newsletter. The purpose of the community is to post a daily recap of activity in fandom."
General Fanfic Communites
blackpearlsails: Fanfic and fanart community for non-slash stories with a rating no higher than soft R
pirategasm: Fanfic and fanart community, for any pairing, genre, rating, etc. (this is probably the most popular piratefic community on lj)
potc_canon_fic: "This community is for Pirates of the Caribbean fanfiction according to canon. Slash and futurefic are allowed, so long as it is carefully extrapolated from canon evidence."
potc_fic: Fanfic community that allows unbetaed stories to be posted, in hopes of finding a beta
potcrps: "The community is mostly for POTC RPS fanfiction, story challenges/requests. Fan art and LJ icon postings are also welcome"
Character and Pairing Specific Communities
_norrington: "For stories prominently featuring Commodore Norrington or Jack Davenport (slash, het, or gen, any rating, any genre, any length), as well as pictures, artwork, icons, and news."
_peasinapod_: Jack and Elizabeth shipper community
barbossa_fic: "This is a community to post Pirates of the Caribbean fan fiction as it relates to Captain Barbossa and his cursed crew."
barbossabeth: "This is a community for the rare pairing Hector Barbossa and Elizabeth Swann from Pirates of the Caribean series"
cutler_beckett: "This community is for all things Cutler Beckett from Pirates of the Caribbean."
davyjonespotc: "Livejournal community dedicated to Davy Jones"
gibbsfanciers: "Here be Gibbs-fancying! Fic, pics, prattling, whatever is welcome"
razor_wit: "This is a community for those rare and distinguished people who appreciate Damian O'Hare; who played Lieutenant Gillette from Pirates of the Caribbean."
gillington: "This community is for sharing the love of this slash couple: Norrington and Gillette from Pirates of the Caribbean. (Fanfictions, icons, fanart, manips, and any other items related to Norrington/Gillette)"
grovesexual: "All stories posted here should involve Lieutenant Groves in some way. Conversation about all things Groves is acceptable as well."
hugmeweatherby: "The only livejournal community for the dashing Governor Weatherby Swann."
jackandanamaria: Jack and Anamaria shipper community.
jackwill: "Anyway, join here if you like CAPTAIN Jack Sparrow, Will Turner, or like the slash pairing of them. Don't worry, we won't kill you if you fancy another pairing. We're very pro Elizabeth. :)"
norribeth: "For everything that involves the lovely pairing of Norrington and Elizabeth."
pirates_bride: "A Jack/Elisabeth [sic] FanFiction Community"
pintel_ragetti: "This is a place where you can post fanfiction, fanart, and discussion relating to Pintel and Ragetti"
potc_elizabeth: "This is a place for meta, art, fic and discussion. If it pertains to Elizabeth, chances are this is the right place for it"
potc_treasures: "This community is for celebrating the secondary and peripheral female characters of the Pirates of the Caribbean movie series"
potcfemmeslash: "Pirates of the Caribbean Femmeslash"
potcot3: "For Jack/Will/Elizabeth fanfic."
sparrington: "A community for all things Jack/Norrington; fanart, fanfiction, icons, fic recs, discussions, etc."
sparrabeth: [Jack/Elizabeth community] "Fic, manips, discussion on the characters in canon--all allowed."
turningpirate: "This community is dedicated to the character of Will Turner from the "Pirates of the Caribbean" movies."
twogoodmen: "A community devoted to Jack/Bootstrap slash"
whore4hector: "a place for we Barbossa fans to sit around and talk about how much we want
willelizabeth: Will and Elizabeth shipper community.
willington: "This community caters to the James/Will pairing."
Communites for Fic, Art, Icon Challenges, Fic of a Specific Length, and Other Activities
piratechallenge: Fic challenge community (seems to be on hiatus)
pirates500: For 500 word snippets of fiction, based on a prompt (prompts are posted biweekly)
pirates_500: "The Pirates of the Caribbean Drabble Archive"
piratestillness: "An icontest community for the movie and cast of Pirates of the Caribbean"
potc_challenge: "Each week, an icon challenge is posted relating to the film Pirates of the Caribbean"
potc_dogwatch: A community to celebrate the PotC fandom with weekly activites and challenges of various sorts
potc_love: "A Pirates of the Caribbean challenge community"
potc100: A drabble community, which once posted weekly prompts, but seems to be on hiatus
potc_secrets: "We are a refuge to all of those thoughts you're afraid to share with your fellow Pirates fans"
Fic Communities Devoted to a Particular Theme
anti_jack: A community for original characters, all based on a piratical picture of Brad Pitt. Originally conceived as a joke, but several writers developed their OCs into well-rounded and interesting additions to the PotC world. (Jacques and Jay are two names used for this character.)
flagitiousabuse: A multifandom community dedicated to stories which feature wigs. For obvious reasons, lots of piratefic can be found there.
cannon_fic: A multifandom community dedicated to stories which feature cannons. Again, lots of piratefic
impofperversity: This community is dedicated to crossover slash fic featuring characters from the film Pirates of the Caribbean (property of Disney Corp) and the novel Quicksilver, by Neal Stephenson
pie_and_honour: A community for PotC fic that features pie or other desserts (pie is a recurring motif in PotC fic).
polyfic: A multifandom community dedicated to stories about threesomes and moresomes. Again, since polyfic is popular in this fandom, you can find lots of PotC fic there
potc_shipfic: This community is for fanfiction, fanart, and discussion about the ships in Pirates of the Caribbean
rnotc: "This Community is fed up with the belief that the Naval characters of the Pirates of the Caribbean franchise are the villains of the piece. This community welcomes anyone who believes in the good nature of the characters as portrayed in Pirates of the Caribbean:The Curse of the Black Pearl."
Recs on crack_van
My "Starter Set" of PotC Recs for folks who are new to the fandom
My Post-DMC Recs
Role Playing Games
Icon and Graphics Communities
elite_pirates: Post any topics related to Pirates of the Caribbean! This includes icons, wallpapers, graphics, discussion topics, screencaps and images."
potc_art: "This is a community where anyone and everyone can share their fanart of this lovely movie here!"
Additional tips for participating in fandom on Live Journal
If you're just joining an existing fandom on live journal, it can be difficult to figure out where to start, where to find the kinds of stories you want to read, etc. This is especially true if you're also new to live journal. The following advice can be applied to any fandom.
Check to see if there are crack_van recs for your new fandom (remember, just because it's not an active fandom there right now doesn't mean it wasn't in the past, or that it wasn't a "featured small fandom" - look in the memories). Check to see if there's a newbieguide for the fandom. Look for a general fic community and see what's available there. If you want to read about a certain character or pairing, look for communities dedicated to that character/pairing and for ship_manifestos or idol_reflections. Ask your flist for recommendation of specific fics and for journals/communities where you're likely to find fic for that fandom. Notice the names of writers you like or people who are clearly involved in the fandom (doing recs on crack_van, writing ship manifestos, modding communities) and check out their user info - what communities and journals are they reading?
You may find that your new fandom isn't organized in the exact same way as your previous fandom, but try to be open minded about any differences you find. Also, it's probably best to do some thorough investigation and ask around before you start creating communities, newsletters, etc. in an existing fandom. It's great to get involved and to participate, but people won't use the resources you create if they're already using something very similar that's been around for a while.