Arcangel is a jack effect for arctan distortion. Sounds nice and grungy without clipping at high levels, and sounds nice at lower levels.
sauditor is a simple, text interface sample auditor with jack output and a spectrum analyser.
todo2html takes standard todo files and generates HTML output with plenty of options for formatting, hiding complete items, etc.
slat lets you play spooky theremin-like tunes with your mouse
powernap gives you accurate sleeping in Python
Perspective demo - the flatland renderer