Box2d Contactlistener

[Noddybear]

Hey guys, im currently working on a game involving Box2d. I have got a physics world working up to the point in which contactlisteners are required for several different objects, and I was wondering if someone could either point me in the direction of some good source material or tutorials involving contactlisteners or someone could just tell me how they are used.
I would post my code exept that it is scattered within about 8 different .as files and is about 800 lines long lol

(btw I have checked out google but there is very little material involving contactlisteners on it)

Thanks a lot xD