The following are some of my personal projects:
Builderoo is a text formatting system for MovableType, the personal web publishing system from Six Apart. Use multiple text filters to quickly build sophisticated blog entries. Change text filters in the middle of an entry. Cache the output of a heavy-duty filter. Create and use macros in your entries.
I originally wrote Builderoo to allow me to include musical score in blog entries by embedding Lilypond markup directly in the entry text. Builderoo provides the infrastructure to have text filters generate images, only generate them once (and not on subsequent rebuilds of the site), and delete them when they are no longer used. The Lilypond plugin and others are included with Builderoo.
[Defunct.] BlogTracker lets you see when your favorite weblogs were last updated, and provides several interfaces for easy reading. Originally known as "The Subhonker Filter," BlogTracker was the first public configurable view of aggregated Weblogs.com "ping" data.
BlogTracker has outlived its usefulness, and has been taken down. Much has changed in the weblog world since it was originally built, and I haven't had the time to give it the attention it deserves. BlogRolling is a similar site, still in operation. More popular these days is the use of RSS feed readers.