Has anyone mentioned Free Pascal? It has an IDE and it can virtually do anything and natively with practically any CPU or O/S. For GUI applications you can use Lazarus IDE and practically most widget sets. Its fully open sourced.

It has a rich ancestry with Delphi and Turbo Pascal, with tons of open source libraries.

Easy to learn, readable code, object oriented, and simply rock solid fast compiled native executables like C, or C++.

I am thinking of making a bitcoin client port to Lazarus, if only I had some time...