I would also be interested in Ruby bindings for this, even if I do have to help write one or make one myself.
I couldn't try out the ruby bindings that are currently up, since it would be hard to integrate into my installation.
But this has been the best library I've seen so far (and I've seen quite a few).
EDIT: I have done a lot of work on this by myself and I have wrapped almost all of the Graphics stuff and all of the Window stuff. All I have left is sound and wrapping everything up.
I did not base my wrapper on the existing rubysfml, so my api will be different. and I also wrapped the C version of sfml since it is a lot easier to work with.