OK here goes *takes deep breath*. I'm listing these recs in no particular order. First up at bat is Lazuli's "Repossession" (
http://lazuli.kat.users.btopenworld.com/repossession.htm). I think it's an incredible piece of writing. It's over 120 chapters long which I believe puts it in range of a King or Michener tome. I've read that others think her Spike and Xander are a bit OoC (especially Spike in the beginning) but I can see them clearly. There are so many memorable bits--William, the splinters, the monster slippers, Xander in the hospital, kilt sex, the MacDonalds and co., Hamish, Bradley, Xander and Angel avenging Spike, the climax and so much more. It's so difficult to describe what happens in the fic so all I'll say is that the road to the bois' true happiness together is extremely bumpy.
Lazuli started writing this in November of 2001(and finished it September 2004). I don't recall exactly when I first read it but it was probably sometime in "The Beginning" which would make it early 2002. I was coming off Spuffy but not used to the idea of S/X and the whole damaged Spike thing sort of squicked me. I found it again a few months later this time falling under its spell. I joined Excessant and stayed with it to it's fabulous end. I've re-read it a few times since looking for the clues Laz planted regarding the finale that become so clear with hindsight. She actually had it all planned out from the beginning!!
There are very few Spander fics (don't know about other 'ships) of that magnitude out there. It's certainly at the other end of the spectrum from drabbles. Looking back there may be a few parts that I feel might have been put in to stretch out the story but I so enjoyed most of them that I'm glad they were included.
Lazuli's site has tried to make it as easy to read as possible. The chapters are divided into 3 parts, there's a partially complete chapter guide plus notes.
Warning: It's S/X, NC-17, h/c, with graphic sex and lots of angst. Be glad if you are about to read it for the first time that it's now complete and you don't have to wait patiently (yeah right) for the next chapter.