To enable the re-use of dotnet assemblies in Silverlight I wrote a handy WPF application called "The Silverlighter". This tool allows you to convert any dotnet assembly into a Silverlight assembly ready for use in your Silverlight applications or class libraries.
The knowledge I needed to write The Silverlighter was gleaned primarily from the excellent article by David Betz called Reusing .NET Assemblies in Silverlight. This article clearly explains how the dotnet->Silverlight conversion process works and why it is not a hack. I thought this article was a fascinating insight into the similarities between the dotnet and Silverlight assemblies and is well worth a read.
But before you get carried away (I know I did) and imagine that you are just a click away from re-using your favourite 3rd party assemblies, a word or two of caution.
Anyway, The Silverlighter app does some cool IL trickery so if you have dotnet dlls you know are fine and just want to use them in Silverlight without any nonsense from Visual Studio then it might be just the thing you need.
There are a few options available to help tweak the functionality.
Finally the path to the ILdasm.exe is exposed just in case you have it at a different location on your system. If you don't have ILdasm.exe anywhere you can get by installing .NET Framework 2.0 Software Development Kit (SDK)