Through Metafilter, I’ve stumbled upon (see what I did there?) a website called Designer’s Couch.
I haven’t spent a lot of time poking around yet, but it seems like a nice, fairly easy-going, non-pretentious place for designer-minded types to post some of their work, get inspired by what others have posted, and to share and to critique.
Of course, like a lot of these communities, there are far more people asking for feedback than giving it. But it’s a nice-looking site, it seems friendly and collaborative, and it has a series of helpful articles.
There’s also some really nice designs up there!