I’m lagging behind the rest of the maths blog community in reporting this, but there is an interesting (and remarkably active) new online maths experiment that has just been set up, called Math Overflow, in which participants can ask and answer research maths questions (though homework questions are discouraged). It reminds me to some extent of the venerable newsgroup sci.math, but with more modern, “Web 2.0” features (for instance, participants can earn “points” for answering questions or rating comments, which then give administrative privileges, which seems to encourage participation). The activity and turnover rate is quite remarkable: perhaps an order of magnitude higher than a typical maths blog, and two orders higher than a typical maths wiki. It’s not clear that the model is transferable to these two settings, though.
There is an active discussion of Math Overflow over at the Secret Blogging Seminar. I don’t have much to add to that discussion, except to say that I am happy to see continued experimentation in various online mathematics formats; we still don’t fully understand what makes an online experiment succeed or fail (or get stuck halfway between the two extremes), and more data points like this are very valuable.