If you want to start writing applications (or widgets) for the Chumby device it helps if you know how to write Flash programs. At the start of this exercise I didn't, and so I had to spend some time in the learning curve.
If you are rich (and a graphics designer) you can simply shell out for a copy of the Adobe developer environment, that lets you create applications using timelines, and all kinds of things that can make things move around the screen. If you aren't rich (but are still a graphics designer) I can reccommend the products from SwishZone that seem to make animations that work, and don't cost that much.
However, I'm not rich. And I'm not a graphics designer, so I wanted to write programs that looked like programs. So instead I'm using FlashDevelop which lets me write programs that look sufficiently like C or C# that I feel mostly at home.
If you want to download the FlashDevelop project and source for my first ever release (Experiment 1: Slidy Clock) you can find it in the downloads part of my Chumby pages. I'll be releasing more experiments as I find out more about how to program this splendid little device.