Like others have mentioned, I mainly stalk remusxsirius and accio_rs_fics and keep an eye on the big R/S fests like this one and rs_games. That has often led me to seek out additional work by authors or artists, and to "meet" some cool people too.

When I first joined the fandom, I was watching Immeritus: The Sirius Black Fan Club (http://immeritus.org/index.php) and found quite a few things there, though I've pretty much stuck to LJ for the last couple of years. I came across imochan's Love Post (http://imochan.livejournal.com/297961.html) a couple of summers ago and spent days on end reading and converting my favorites to read on my Kindle (including a couple of great short pieces by mindabbles if I remember correctly). I've found that overall quality of stories in LJ, at least in my experience, has been higher than on places like fanfiction.net.