OSGi in Practice

So I was thinking about writing a modular program in Java. By modular I mean extensible via plugins, a l Firefox, Chrome, Launchy, etc., but of course on a simpler scale.

I got into reading about OSGi for this purpose but I don't find that it makes a whole lot of sense to me. I think this is because I can't quite understand how this fits together for my purpose. I hear a lot about writing plugins, but how would I go about writing the *core* to make it extensible via plugins?

Help would be appreciated. Read a whole lot and learnt a whole little.

Sepples
Stop wasting your time on gimmick technologies. It's incredibly simple in sane languages like C and Python.