I created a pretty basic module using VS 2005 express edition, that installs and runs perfectly on 4.08.  If I wanted to get this same exact module to install on release 3, what are some high level things I need to be aware of in order to create a similar working module for release 3?  I understand there is a lot of 'it depends' in that question, but any helpful links or documentation explaining the major differences will be helpful.

I beleave that the ASP framework is the main difference.  I think there is also some differences with what goes into the final module package.

This might help

http://www.seaburydesign.com/Tutorials/DNN3xModuleCreation/tabid/67/Default.aspx

Mike