Moonlight is a GPL'ed open source implementation of Silverlight, created by the Mono team at Novell. While it's a Novell project, we're helping them out, and I'm excited at the progress that they've made, and that we'll have a free software playback option for Silverlight.
Here's a list of supported sites. I imagine most of my demo projects up on Silverlight Streaming should work, as they're all Silverlight 1.0 compatible at this point. Someone who gets this installed, let me know (my personal lameness documented below).
Ars Technica also has a good article about beta 1. It contains plenty of screen shots and such, which I have once again failed to provide due to my lamentable lack of Linux-fu.
Anyway, huzzah to the Moonlight team. I can't wait for the final release of Moonlight 1.0 and the first beta of Moonlight 2.0.
(Yes I did try to install Ubuntu, but as with every attempt I've made to run Linux in the last five years, I quickly got stymied by video driver issues. While I got basic display working, I was using my backup Barcelona box, which has my beloved but ancient LaCie ElectronBlu 22: CRT monitor and a cheapo 1280x1024 LCD. Out of the box, it wouldn't let me run the main monitor at more than the small displays resolution or (more painfully) refresh rate. I tried to fix it until I got to the "type sudo..." phase. I bumped into Miguel de Icaza himself at an event last week (we had a fun chat about GPU compositing), who tells me that the new OpenSUSE 11.1 has a nice GUI configuration utility that should fix the issue.)