Eyeing Up EyeOS
A year ago, I would have dismissed the idea of a Web-based desktop as pretty pointless. Today, spending as I do around 99% of my time within Firefox - browsing, using GMail and Writely - I have to admit that it has a certain logic.
EyeOS bolsters its case by adding two crucially important features: it's free software, and it doesn't use Flash. There's a demo for you to try it out, as well as a begging bowl - they need some dosh to move the project on.