Is this group currently active? What are meetups like?
Yes, we're still active. A typical meetup is 4-6 people discussing rationality and other random topics, and perhaps playing rationality-oriented games, for about four hours. The full schedule and mailing list are on the meetup.com page. The next two are on Thursday 21 Apr at 7:30pm, and Sunday 1 May at 2:00pm. You should come, we'd be glad to have your company.
The Sunday Cambridge meetups, which happen on the first and third Sunday of each month, are now at 2:00 pm at Cosi, near Kendall Square. As discussed at the last meetup, we've changed the location because the old location was becoming too crowded, and the time to allow the meetup to go on longer before people have to leave.