I have known about CiteULike in a vague sense for some months, but only recently have started to use it. I was inspired by some training I did on Reference Manager recently; to make it a little more exciting, I thought I'd throw the idea of social software and shared citation database in at he end. Then it occurred to me that I really ought to be using it myself.
So you will soon find a CiteULike link in the sidebar.
http://www.citeulike.org/user/tomroper