They seem obvious recs, but have you read these two series (they both span seasons and are essential reads)...
The Origins series by Niamh (Origins, Origins : bridge, Origins Revelations, Destinies, All I Want Is You, God Only Knows, Family, Origins Resolutions, Small Hrs (WIP but a ficlet)
Post The Gift; Life surviving without Buffy and the consequences of her return. . .The Yellow Brick Road series by Holly (Cupidity, Nemesis, L'Amour)
A series rewriting Season 3, beginning with an alternate version of Season 3's Helpless, in which the Council locks a drugged and powerless Buffy in with a certain bleached-blond vampire who already has two Slayers under his belt. Continues there in unfolding Spike and Buffy's journey through acceptance, trust, and eventually love.This series might also work...
To Kill This Girl by Sandy sequels
You Have To Love Her and
Double Trouble Spike agrees to leave Sunnydale...for a price.What was it about Gem Of A Soul you particularly liked?