So far there's a few forums for these new online classes, like the AIqus site[0], Udacity forums for CS 101[1] and CS 373[2], and a lot of IRC channels, the main hubs being at #free-class, #udacity, and #mitx on irc.freenode.net[3].
There's individual channels for each course as well, for Coursera courses they follow the pattern of the class url preceded by an octothorpe, so for the Design and Analysis of Algorithms I class at http://algo-class.org for example, the IRC channel for it is #algo-class. For the Udacity courses, they follow the pattern of ##udacity-<course number>, so for example ##udacity-cs101 and ##udacity-cs373
Anybody wants to create hn one for algorithms/nlp? Might come up quite useful.