http://www.facebook.com/Whenareyougoing?ref=ts. <--- This page is set up for all those who are starting their training at HMS Raleigh to meet and get to know each other before the start date. Just post your date and chosen job on the page wall to join the list
I would say that there are 2 things you would want to address when doing this sort of thing. A: can anyone else (ie, the public) see the group? make it a private or secret group, and B: how can you verify those purporting to be joining with you?
FB is a good tool for communication, and I'll admit to having a couple of RRers on facebook, but you might want to be a bit more careful.