Matt Sprague and I have put in a bit of work making OpenBabel accessible on the .NET platform on Windows (see Matt's recent post, for example). .NET is like Microsoft's JVM. There are several .NET languages (e.g. C#, Visual Basic, IronPython), just like there are several languages for the JVM (e.g. Java, Jython, JRuby). If you write a program in any of the languages and compile it, the resulting classes can be used from any of the other languages.
Having finished the work for Windows, I started to look at Linux and MacOSX. There's an Open Source version of .NET called Mono, which is available cross-platform. After a bit of hacking around, I'm pleased to announce that the next release of OpenBabel will provide support for Mono on Linux and MacOSX. I've included an example C# and IronPython script that uses OpenBabel (see here).
One thing I was wondering though: anyone have any idea how widely Mono is used?