Widgetropolis has a growing collection of widgets for Twitter:

Multitwit – Adobe Air for multi-account tweeting
Twitter follower widget – straight html for webpages
Twitter friends widget – straight html for webpages
These are not fancy but do exactly what they say. Might be worth investigating for a light app and simple code.

There is one other bonus item they have that is non-Twitter related. it is a piece of javascript that acts as a webpage hand grenade. You need to visit to see it, really. Brilliant.