Five great stories by Indri
Foreign Devils. PG-13. Written in 2002, before the character was given a name, this is the story of the Chinese Slayer.
Descent. R. A newly souled Spike spirals down the path of madness with a little help from the First Evil.
Return. PG. Fred goes home, post-NFA.
The incredible, wonderful Halfway There. PG. What happened to Giles in season 7.
Ethan Rayne vs America. PG. Ethan's time with the Initiative.
And once you've read all those (and everything else on indri's website), make sure you read her Giles/Ethan Novel, In the Morning of the Magicians. Rated mature for sexual situations and drug use.