I've heard of other LessWrongers using Google Hangouts for this and various personal projects, with all kinds of rules or variants fished from various GTD-related strategies.

Personally, I'd be interested in setting up an IRC chatroom, google hangout or other semi-persistent thinghy for pair/group-studying of... well, I'm not sure what yet. I'm looking at the courses in the MIT Challenge, reading through the first book of Feynman's Lectures (since it's finally available for free online here, which is the only place I've ever found it for less than 200$ /w shipping), other FAI/MIRI course, or whatever else ends up on top of the list after my current round of priority-realignment is over.