Readers who are especially sharp-eyed or looking for that sort of thing might have noticed that my sidebar contains a section called 'places to talk veganism'. The links basically do what it says on the tin. They are all places, broadly speaking, for vegans to talk about veganism. This does not mean they are all the same! So, for the benefit of anyone new to veganism in general or online veganism in particular, here's the lowdown...
Vegan Forum is the most active board I've found so far. Discussion tends to be at a civil and friendly level, with very little deliberate sh*t-stirring. Has a specific section for people who aren't quite vegan (although the expectation is that you'll get there sometime, preferably soon). This is generally my favourite online vegan hangout as it a) encompasses a wide range of discussion topics and b) seems to be about constructive discussion rather than points-scoring. If you're a new vegan finding your canvas-booted feet, this is the place I'd recommend.
Vegan Fitness, as the name suggests, is focussed on fitness, sports and exercise, with a vegan slant on things. My sometimes-enthusiastic and mostly half-arsed attitude to such things means that I welcome the encouragement you can get from such a place. It also has ethics, activism and general discussion sections. The best place to go to talk about nutrition, training diets and so on.
Vegan Freaks: abolitionist message board with probably the strictest screening process out of all the ones listed here. Can be fun and interesting, but not for the faint-hearted or anyone who isn't 100% sure of their commitment to veganism. Best place to go if you want tough love.
Vegan Represent: I don't hang out here as much, partly because it's quieter and partly because I signed up for it after becoming vaguely established in a couple of other places. Seems like a pretty good atmosphere, though.
Vegan Buddies: kind of quiet, but a good place to go if you're a new vegan wanting advice on certain matters, especially if you're scared your question will look 'stupid' on other forums. NOT the place to go if you like trashing less experienced vegans. (actually, neither is this - *sticks out tounge*)
There are also a number of yahoogroups. I haven't been on any of them long enough to review them, but expect a post at some point.