I'm looking for some good websites with fairly large communities of people into photography where you can go to pick up tips and advice. Somewhere where you can post a few photos and ask for advice on what went wrong, tips on getting the right exposure, etc.
I'm a member of Flickr and find a few groups on there useful, but generally they're not that busy. So what are some of the other good sites?
One other thing, where are some of the best places for regular competitions where I can submit some photos?