What flavor is a blog roll, anyway, and is it good with butter?
Fanfic archives
A Teaspoon and an Open Mind A Doctor Who fanfiction archive, modded and sporting an advanced search. Tasty.
The Gossamer Project I don't read X-Files fic much any more, but it's Gossamer.
Fanfiction.net Mmm, obligatory. Also home to the horrible ellipses-filled versions of my oldest works...and now some newer things!
Reference - Writing
little_details A LiveJournal community dedicated to asking all those questions Google can't quite answer. A LiveJournal account is required to post, but not to browse, and it's well-tagged.
Writing Realistic Injuries Brief but useful descriptions of many ways characters will end up maimed in action.
Cut and Thrust of Blade Combat What it says on the tin. Fairly descriptive of the mess blades will make of a human body, so avoid if squeamish (why are you writing sword combat then?).
Oi! Yanks! No! Useful for Americans writing British characters.
A Dictionary of Slang for the UK. Fun times.
Erowid Tons of information and personal accounts of experiences with psychoactive drugs, useful if one of your characters is going to be ingesting them.
May be NSFW in the sense it discusses...welll, drug use.
Reference - English
Dictionary.com and its Thesaurus buddy. The ads are a bit annoying, but for checking word use and thesaurus adventures, it's very handy (especially as you can add it to Firefox's search).
OneLook Reverse Dictionary Try and find that word where you know what it means...but can't remember what it is. Sometimes gives odd results, sometimes gives the perfect "aha!" moment.
The Elements of Style It's an old version, but a lot of the advice still stands. Requires a bit of basic grammar-term-fu to grok, but also has examples.
Common mistakes in English Simple and useful explanations of many points of confusion.
The Big List of Fanfic Peeves Despite the title, is useful for writing in general, as it covers grammar, punctuation, and other basics.
May be NSFW, as it uses examples from smut.
Other
The Drabble Project, featuring info and examples on the origin of the term.
A Guide to FF.net's War On Punctuation Fanfiction.net is infamous for stripping a lot of things. Here's what will vanish (and sometimes how to get it back).