Recolino
Recolino is a real-time command line annotator. It can be used to annotate audio files by listening and simultenously tapping on either the PC keyboard or a MIDI device.
Ecasound
Ecasound is a software package designed for multitrack audio processing. It can be used for simple tasks like audio playback, recording and format conversions, as well as for multitrack effect processing, mixing, recording and signal recycling. Ecasound's main author is Kai Vehmanen. My main contribution was the Ruby interface to Ecasound.
Some years ago I also started to code a graphical user interface to Ecasound, which is called Visecas. It is written in Ruby using the Ruby-Gnome2 bindings. You may consider it abandoned.
Lamaga
Lamaga is the lazy man's web gallery, which I wrote in 2004 (very pre-web2.0). Place all your images in a directory tree, fire up lamaga, and it will automatically generate an HTML gallery. Lamaga is written in Perl.
Fifi
I happened to stumble upon this gem when I cleaned up an old hard disk. Fifi is a GUI for find and grep, which I wrote in 2002 as a tiny excercise in Tcl/Tk. When I only recently rediscovered it, I was amazed to find that a) it still works out of the box (kudos to Tcl/Tk) and b) it is indeed useful. Anyway, decide for yourself: