This was my main association. And "camp" has a sort of kidd-ish association for me. I feel like kids go to camp and adults go to retreats. Not sure how representative this is.
How about "workshop"?
I agree about the kiddish vibe of "camp" and I also agree that "retreat" has a sort of religious hue to it as well. Some guy died on a "mysterious Buddhist retreat" recently.
The new Center for Applied Rationality website has launched! We'll be adding content as time goes by. Let us know if you find broken links, etc.