Can you provide the best resource, i.e. guides, articles, documents, links, videos, to migrate from Visual Studio 2005 to Visual Studio 2010, in other words from .net 2.0 to .net 4.?
MSDN is the best place for anything relating to the .net framework, more specifically:
New To Development?
How Do I? Visual Studio 2010 Videos
Learning Visual Studio
I'm not sure which language you develop in, but the transition isn't likely to change your code (if you mean refactoring) since .net is mostly backwards compatible. You may wish to expand your current software to use features only included in a newer .net version, see "whats new".