could anyone tell me what are the best software packages to use when programming stuff like Nmap or Back Orifice
If you're looking for something like Visual Basic for crackers, you'll be disappointed.

Nmap is written in spaghetti C and is a very complicated program. Not only is what it does fairly difficult, but it tries to do it all in the same program.

BO is AFAIK either written in C or C++. Although what it does isn't rocket science, the implementation is reasonably clever.

Many tools are simple, but these two are certainly not. Nor are they things that you can code without a great deal of experience. IMHO, programming language and/or tools aren't really important, just experience and knowledge of the underlying systems (i.e. Windows for BO) or protocols (f.e. TCP, UDP etc for nmap)

You aren't just going to sit down and create the next super-scanner