Sirius alread has a crush on Remus, and tells him about it. At one point he leaps onto/tackles Remus, and Remus falls off his bed and hits his noggin on the nightstand. (I've written up to here) Sirius spends the whole rest of the fic trying to figure out if Remus has a case of temporary amnesia, or if he can actually remember Sirius' confession. And I have no clue how to actually write this last part!
Er. . . when I write it down, it looks kinda pathetic. It sounded a lot better in my head, I swear!
Oh, and I'm always a sucker for OoTP-era fics where Harry finds out about Remus/Sirius. No specific plot bunnies for that, though. YET.