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You'll be able to use Ruby and Python to languages for you to create rich Internet application (RIA) in Silverlight on the client side. Ruby and Python are among the dynamic languages supported in Silverlight using the Dynamic Runtime Library (DLR).
You can read more about the DLR and Silverlight at Scott Hanselman's blog entry, Iron Python and the DLR march on. You'll find a great resource list there too.
Silverlight 2 is to be released later this calendar year. You can get the latest beta from the Silverlight developer site. You can learn more about dynamic languages with Silverlight at Silverlight: Dyanamic Languages. There you'll find samples, quick starts, and link to the Silverlight Dynamic Language SDK.