DirectFB is a thin library that provides developers with hardware graphics acceleration, input device handling and abstraction, an integrated windowing system with support for translucent windows and multiple display layers on top of the Linux framebuffer device. It is a complete hardware abstraction layer with software fallbacks for every graphics operation that is not supported by the underlying hardware.
PLplot is a library of C functions that are useful for making scientific plots from programs written in a wide variety of languages. It can be used to create standard x-y plots, semi-log plots, log-log plots, contour plots, 3D plots, shade (gray-scale and color) plots, mesh plots, bar charts, and pie charts. Multiple graphs may be placed on a single page with multiple lines in each graph. Different line styles, widths, and colors are supported. A virtually infinite number of distinct area fill patterns may be used. A variety of output devices and file formats are supported.
py-xmlrpc is an extremely fast implementation of the xmlrpc spec for Python (written in C). It supports both blocking and non-blocking clients and servers on Windows and POSIX platforms. Version 0.8.1 is 100% compliant with the xmlrpc validator found at http://validator.xmlrpc.com.
SuperTux is a side-scrolling platform game. The hero in this game is Tux the Penguin, the game's only reference to Linux. On the journey to rescue Penny, who has been kidnapped by evil Nolok, Tux faces 23 different kinds of bad guys while jumping and running through 101 beautifully-drawn levels. The soundtrack is available on last.fm and similar sites.