I'm looking for this fic. Its post Buffy and Xander somehow is a seer and that's his function in the national "scoobies" orginization. Spike is a gohst (The PTB charged him with looking after thbe baby slayers, somehow he can kill demons in his form). He starts to be able to communicate with Xander. Then Xander tells everyone that Spike's not gone, that he can see and hear him. At frist they don't beleive, but then at the near the end of the fic, Willow magics a ring that makes Spike corpreal, so that every one can see, hear and feel him but he's still a bit glowy.
ANway, the main deal was the slow buddin relationship between Spike and Xander... *fangirl squee* it was so cute.