c64-network.org is a networked version of the Frodo emulator, where you can play C64 games against other people over internet. It also has a port to Nintendo Wii and a custom GUI with game information, a virtual keyboard etc.
Detox64 is an application which translates C64 BASIC files to readable text.
A graphical temperature monitor for Linux.
A tool for preparing HTML slides with LaTeX formulae.