Jmol is a Free, Open Source molecule viewer and editor. It is a collaboratively developed visualization and measurement tool for chemical scientists. Jmol is an active project, and there are new features being added to it on a daily basis. Users are encouraged to modify it to fit their needs and to contribute their changes to the project.
The LinuxClassLibrary is a growing set of classes which everyone needs every day, that runs on all types of *nix and also on Win32. Currently it is a library that works in the background (non GUI). Current features are character handling, file descriptors (sockets, file, etc.), a database system (like the Perl DBI), an event system, template collection classes (set, heap, hash, etc.), IPC, protocols, plug-ins, and images.
libmikmod is a portable sound library, which used to be packaged with the MikMod module player, but is now released independently. It is capable of playing samples as well as module files, using the OSS driver for output, as well as ALSA and EsounD. Supported module formats include MOD, S3M, XM, IT, MED, MTM, and 669, to name a few.