ClanLib is a cross-platform game SDK currently supporting Windows and Linux. It provides easy-to-use interfaces for 2D graphics, input, sound, resources, networking, GUI, OpenGL, and more. The goal is to provide a game SDK that does all the dirty work that all modern games need to implement anyway, thus making the game developer concentrate on the gameplay instead of reinventing the wheel over and over again.
Information regarding Project Releases and Project Resources. Note that the information here is a quote from Freecode.com page, and the downloads themselves may not be hosted on OSDN.