Here's the webinar platform I may be using for CUE, CLMS, and Wikispaces this summer. It's particularly good for sharing the web – and demonstrating web 2.0 sites to participants. :) "Web conferencing that just works. Dimdim provides easy, open, affordable collaboration. Use for online meetings, eLearning, desktop sharing, training, distance education, unified collaboration, webinar, free web meetings and more."
GROU.PS :: connects obsessively!
Here's a free and ad free alternative to Ning for creating your own social network. I only poked around but it looks easy and feature rich. And this is a bonus: "GROU.PS is free! You pay nothing. Plus, we don't force you to show your community our brand and/or our ads unless your storage needs exceed 3GB." Thanks to Kevin Jarret for sharing this on twitter.