I'm not sure how I feel about the whole "same syntax as jQuery UI only slightly different" class structure. Maybe change to an "fb-" prefix?

Please consider adding dropdowns, popovers, modals or form elements :)

There's been an issue for dropdowns since may [0], but there hasn't been much activity in the repo. I guess you could fork it and add it in yourself, or use it in combination with the fb-bootstrap posted. I would fork it and add it myself, but I'm not good enough at web design to do so.

[0] - https://github.com/necolas/css3-facebook-buttons/issues/1

Check out http://ckrack.github.com/fbootstrapp/

I rewritten this in SCSS and Compass, and added some dropdowns, check them out here: https://github.com/andrei4002/facebook-buttons