Is their PMing on this site to talk to people? If not it should be added to people could make friends and use this site to communicate to existing friends. Also a comment notification should pop up near your avatar to show that you have an unseen comment, with this you would also need to add a feature to mark comments as seen.
You can comment on people's profiles. As long as they're receiving e-mail notifications when they get a new comment and are constantly checking it, you can PM that way. Keep in mind, however, that comments are viewable to everyone. (No pop ups, you just have to keep your e-mail open.)
Members may have IM programs. Upon glancing at your profile, perhaps finding someone else that has Y!IM, or getting an AIM account or MSN will widen the spectrum of those you can interact with.
Sorry, mate. That's what your options are. There are some usermade chatrooms, which can be found on this page of the Chat System thread (per Knight).
