This post is somewhat nostalgic for me because these were the fics I was reading early on in my lurker days before I had an LJ or was writing. Each of these stories are excellent and although they are permanent WIPs, you won't be disappointed with the plots. They range in chapter length from 10-47. Most written during or prior to 2006.
1.
A Dying Dream by Europanya (
euro_fics)
RATING: NC-17
SETTING: Canon through BtVS, AU for AtS S5
PAIRING: Buffy/Spike
SUMMARY: A decade after closing the Hellmouth and doing time in Hell, Spike is living in San Francisco, a lone vampire in a world nearly wiped clean of demons, when Buffy unexpectedly finds her way back to him. [19 chapters]
2.
Marking Time by
annapurna_2 RATING: NC-17
SETTING: Post-NFA
PAIRING: Spike/Buffy
SUMMARY: Buffy receives an unexpected summons to England where she learns she's not the only one with nine lives. But a mysterious crisis threatens. How far is she willing to go to save the vampire she loves? [16 chapters]
3.
A Soul to Seduce by
eurydice72 RATING: Eventually NC-17
SETTING: Immediately after the AtS S5 episode "Damage," but veers from canon.
PAIRING: Spike/Buffy, Wes/Faith, Lindsey/OC
SUMMARY: When Buffy finds out that Spike is alive, she shows up in LA to demand answers, only to find herself immediately immersed in a web of deceit and betrayal. Who to trust becomes the million dollar question, and her life turns into a race to solve it... before it's too late for everyone. [23 chapters]
4.
Shot in the Dark by
Tiana RATING: R
SETTING: Season 4, Post-Doomed/A New Man, except there is no Riley
PAIRING: Spike/Buffy
SUMMARY: Cupid, on a bet from his live, Psyche, decides to play matchmaker with our two favorite mortal enemies: Buffy and Spike. [47 chapters]
5.
The Sweet Spot and its AU sequel by
Rabid1stRATING: NC-17
SETTING: Shortly after Older and Far Away, but Pre-As You Were
PAIRING: Spike/Buffy with magic-induced gender-swapping
SUMMARY: Spike and Buffy take some time to explore each other after the Dead Things beating and their rocky reunion of OAFA. An evening of magic and its unexpected consequences, teaches Buffy a thing or two about motivation and convenience. [10 chapters]