Application Development using Eclipse Framework

Hi All.

I am about to start a new development project. I would like to use Eclipse as the shell of my application (i.e I dont want to develop with Eclipse necessarily, but I want my application to be built on top of eclipse - as I'm sure lots of applications have already - ones I know of being Siemens Team Center, Sparx Enterprise Architect and Medini Unite).

Can somebody please point me in the right direction to get started? Ive hunted around quite a bit, but there's so much to do with Eclipse I'm not sure I'm looking in the right place and dont want to start going down the wrong path!!

Many Thanks

BW