ClanLib rocks! I've been using it for a while and my project is happily running on the "big three" with it. (Win, OSX universal binaries, linux) I would recommend it to people who are very comfortable with C++ and concepts like sigslots. It's great, but the docs are thin so getting into the source is required to find info sometimes. We're working towards a final 0.8 release soon (a week or so?). If you want to play with it before then, I recommend working directly from SVN as the release candidates up for download are outdated.