SDL is a good library but if you are looking for something a bit more advanced try ClanLib. I supports pixel-based collision detection which works very well and you can use it on virtually any platform if you have the time to read the cross compiling documentation they have on the website.

I also suggest DirectX ... I made a 2D game out of it myself, its in the Showcase, Galaxy Gladiator, DirectX still has all the 2D drawing calls from previous versions, and if you want D3D also can do 2D games, simple make all the 3D object 0 deep and have your textures maped to the facing side. DirectX also has alot of handy calls built into the api to make alot of stuff easier, like buttons and clicking events ... if you dont know much about directX Introduction to 3D Game programming with DirectX 9.0 by Frank D. Luna its a wordware game and graphics library book, they even use it in programing courses