There's a new Sirius-centric community on IJ! If you've been longing to pair Sirius with someone other than Harry (Why? Why?
Oh, wait -- I've done that!) or write about just Sirius, check out Sirius Lovers
From the userinfo:
This is an asylum for all your Sirius needs. Here you can post Sirius Black fiction, art, meta, drabbles, essays, threesomes, foursomes, crossovers, AU, AR, crack and basically anything about Sirius Black. Sirius must be the main focus of all posts. Story searches, story recs and beta requests are also allowed.
See the link for community rules.