I've just noticed that Gmail has started offering Facebook Connect within the site itself. While reading an email, a box appeared with that person's details, with an option to connect in Facebook.
And there's also a box at the top right of the Gmail screen letting me connect to view and update Facebook status messages from within Gmail itself.
Nice! Is it brand new, or has everyone else been using this for a while? EDIT - Oh, I think it may be to do with Xoopit, the image plug-in thing I installed and forgot about a while back, not Gmail itself.