R/S have indeed made it to tumblr! In a small way, if you follow the right people. And/or track the Wolfstar tag. Also last year in December they started a Shoebox Reread Project where everyone reads one chapter a day until, well I guess, the 23. I didn't participate, but hopefully I will this year?

I watch accio_rs_fics here, and the rs_games. Many of my old favorites are/were at FictionAlley, though that site is quite slow anymore. When I actively seek out new fic, I usually hit ff.net and hope there's some decent new things, and I'm moving slowly toward AO3, having been introduced to it recently.