Hey Hey,

Development:

C/C++ == on *nix you're going to use Vi (Vim) for your IDE and gcc and g++ for compiling... On Windows.. Bloodshed Dev-C++ is probably your best bet for an IDE... you can get gcc and g++ for Windows... (It's one of two compilers that Dev-C++ will interact with... the other is dgjpp)..

C# == You'll have to go with mono..

Virtualization..

VMWare -- Cross Platform... Server and Player are free
Virtual PC --- Windows / Mac... certain versions have been released free of charge.
Xen -- not really for running a Windows VM
Qemu -- Emulation not virtualization... not bad for *nix command line but that's about it..

I recommend VMWare personally

Peace,
HT