Here are some links to sites that have a collection of Buffy/Willow stories - Bwriter
IKOLY - a great B/W archive
Bloody Summers Tales - Another good Site with crossovers - more conventional pairing tho
BearCave - A great collection of Buffy/Willow stories
Mystic Muse - a great site with all pairings
Kinetic-kid - a great site with different f/f pairings
Happy Little Minion - A great Buffy/Tara site
Twisting the Helmouth - A great collection of Buffy Crossovers
Rebelrsr's Fics - Some good Buffy/Willow fics