Clocks of the Long Now is an excellent ensemble Spuffy fic set some years post-NFA in which the Scoobies have drifted apart, but must band together once again to avert a Slayer civil war. It's got action, adventure, boatloads of humor, angst. Basically, it's got pretty much everything, and plus two bangin' original characters you don't want to miss. Go look and give lostboy some love.
Family Reunion is a really, fascinating and excellent ensemble AU set in London following the lives of Spike, Darla, and Connor as the youth destined to lead demon-kind in world destruction. Their is tons of action, intrigue, and at least a mention of pretty much every darn main character to grace Angel or BtVS. Run, don't walk.