The final version of Silverlight 1.0 and Silverlight 1.1 Alpha September Refresh have just been released to the web. They are available for download at http://silverlight.net/GetStarted

It's worth noting that Microsoft has established a formal partnership with Novell to provide a Silverlight implementation for Linux in the next few months.  Microsoft will be delivering Silverlight Media Codecs for Linux, and Novell will be building a 100% compatible Silverlight runtime implementation called "Moonlight". More detail at Scott's blog.