I recently heard of Konfabulator www.konfabulator.com when reading that Yahoo had bought them and they're going to be renamed Yahoo! Widgets
Konfabulator implements a pretty slick concept of "widgets" that are what you want them to be.
Messing around with a widget I downloaded last night proved to be highly addictive.
They have a lot of widgets in the widget gallery.
I intend to release the updated Radar widget that I worked on last night.
Check 'em out, you'll like 'em.