I know I sound like a broken record, but just so it's out there:
Visual Foxpro 5 and 6 IDE's DO run under Wine, BUT, left mouse clicks in child windows are broken. I've compiled and run VFP apps under wine, but it's a pain in the butt to go kybd only in a Visual IDE :P
are you volontairing ?
Sorry not to answer your main questions, but some ideas on this ... We use gcc, wxWindows and mingw. Not sure how much you _need_ .NET but we migrated our (fairly complex) app from Visual C++/MFC to wxWindows and it was definitely worth it. Also we can use gcc to cross-compile from Linux for Windows, so basically although our software is currently used exclusively on Windows, I can develop it all on Linux (obviously some testing to be done on Windows as well, but basically it works). And it's all free, open-source software. I'd recommend checking it out.
this combined with mono might give you just enough to develop .NET progs under linux.
Mark Hannessen