General or Assorted Fan Fiction
Slayer's Fan Fiction Archive Great place to start out. Tons of stories for both shows, but its hard to find anything specific.
Sonja Marie's Buffy Fan Fiction Links Ultimate links resource. You'll usually find what you're looking for here.
Unconventional Relationshippers Archive for the UCSL list.
Pink Rabbit Consortium F/F Slash for all fandoms. Has great quality Buffy, Xena, Voyager, and more.
Sapphic Slayer Homepage and archive for the list with the same name.
Buffy-Beta Archive Find the fic from the Buffy-Beta (general fiction) List here.
Slash it Up! Indexing for slash sites.

Character and Pairing Fan Fiction
Faith Rocks Great resource for the best Faith fiction. Most of which is Faith/Buffy.
CordySlash Kind of says it all. Nice layout, good fiction.
aSlayer, aHacker Site dedicated to the pairing of Buffy and Willow. Focus on fiction and artwork.
Slayer Pride Awesome Faith/Buffy site. Tons to keep you busy.
Blue Lights Buffy/Dru archive.
Willow/Tara 'Shipper site with pictures, links, and more.
Wiccan Ways Willow/Tara fan fiction archive

Author Sites
Empty Mostly Buffy/Willow.
Human Drama Series by Kate Bolin.
Kimber's Corner Kimber's personal site can be found here.
All Mine An ongoing series involving Faith and Dru
Freelance Spice Some awesome Buffy and Faith fiction.