Those readers of the Microsoft Studentzine newsletter will have seen Ben Coley's series of articles helping you create your first game using XNA. He's walking readers through the creation of Pacman adding new code and gameplay each month. His first two articles can be found below but if you want want to keep up to date with this and other tech tutorials you should sign up to the Studentzine here.
Dom Green, a MSP at MMU (and soon to be Microsoft employee) has taken Ben's example and ported the code to Silverlight v2. Because Silverlight v2 uses .NET and C# it is very easy to port content from other .NET platforms such as XNA especially if (as in Ben's example) they're not using to many (or any) platform specific libraries. In fact Dom has taken it one step further and implemented functionality which Ben (as yet) has not ;). I think this should be an official race... who'll get a fully fledged version of Pacman live first, Ben on XNA or Dom on Silverlight; only time will tell!
(A word to the wise - If you have the Silverlight v1 runtime installed make sure you manually uninstall it before installing the v2 beta 1 required to view Dom's demo)