I recommend the Silken Cage Series.
Duck's Fanfic
Great fic, great graphics, and a great message board.
Cruel Obsessions
Very intense Buffy/Angelus fic, great mailing list. May have to refresh.
Organized Insanity
Fic for pretty much everybody.
My Immortal Beloved
Great slash fanfic.
Fanfiction.net
New fic submitted daily.
The Slayer's Fanfic Archive
Fic for everyone
Eternal Nightcap
Lots of Spike/Angel stuff.
The Days of Our Unlives
Very hilarious Spike/Angel fic
Save Your Soul
Very big selection of Buffy/Angelus fanfiction.
BitchEnvy
Lots of adult B/A, B/A(us), and other pairings
Every Six Seconds
Gia's wonderful B/A fic