Comment libSDL (Score 1) 531
You may know about libSDL on Linux, which has been used in many Linux games. Loki has also succesfully ported across several Windows games to it. Don't be fooled by the name "Simple DirectMedia Library": Simple doesn't imply 'restricted', and 'DirectMedia' doesn't mean that only abstracts multimedia capabilities.
libSDL is a cross-platform library which supports not only video and audio, but also threads and timers. There are also plenty of support libraries for it -- including a cross-platform networking library that works on Linux, Windows, MacOS and BeOS. There's plenty of example programs for you to work with, it's open-source, and perhaps most importantly, it is mature and tested. The only downfall of it is that you'll have to track down the documentation for it, but there are plenty of SDL gurus around if you know where to look (the SDL mailing list is a great start). The SDL homepage itself also has links to other similar ambitious libraries, such as clanlib, if you don't like it. I definitely recommend that you check it out.
