Mindy,

If you want to do .NET development for Mac OS X 10.2 then you could use Microsoft's Shared Source CLI (Rotor) which is pretty good.

http://www.microsoft.com/downloads/details.aspx?FamilyId=3A1C93FA-7462-47D0-8E56-8DD34C6292F0&displaylang=en

http://www.sscli.net/servlets/ProjectList

As for WinForms, the implementation is pretty much entrenched in the current Windows architecture (WndProc) and wouldn't be directly compatible with the way the Mac (Aqua?) does things.

Mono gets round this by using a WinForms implementation that utilises Wine to thunk/emulate the P/Invoke and WndProc events.

HTH
Neil