Moonlight is an open source implementation of Microsoft Silverlight for Unix systems. Ubuntu 10.04 LTS already has it in the repository.
sudo apt-get update
sudo apt-get upgrade
sudo apt-get install libmoon moonlight-plugin-mozilla moonlight-plugin-core
or you can go to their website http://www.go-mono.com/moonlight/ and install the Chrome extension or Firefox plug-in.
You'll need to restart your browser for it to take effect.
Update: Moonlight does NOT support DRM content. That means no Netflix.