The second 2.0 platform of the day is Hypertope. I was kindly informed about this via this blog and I just subscribed. Finally, something specifically for academics. I'm a bit nervous about having to maintain another webspace, but maybe it'll be easy to combine. It certainly looks very interesting. They have a free join-up for a limited period only, then it's by invitation. PS: thanks for the correction guys ;)  hyperTOPE, not hyperTROPE! got it. at least, the link was accurate :)