I have started creating ASP.NET 2.0 versions of my commercial products, AdMentor and KBMentor - and one of the the most important goals I have is having them run under medium trust.
Here I have published some of my findings:
http://www.aspcode.net/articles/l_en-US/t_default/ASP.NET/ASP.NET2.0/Medium-trust/category_69.aspx
I have also created a GPL project with the goal to offer a recompiled version of the official MySQL.Data.DLL driver - just adding the [assembly: AllowPartiallyTrustedCallers()] attribute so we don't get the "Additional information: That assembly does not allow partially trusted callers" error.
Information and downloads for that project is here
http://www.programmingado.net/l_en-US/t_default/MySQL/Medium-trust-ADO.NET-driver/category_10.aspx