Chipmunk lacks some docs, so I need to dig into it myself.
I hope someone can help me with a few Questions.

What exactly do the numbers to for the gravity?
In a sample the author sets it to 0,-100.
What exactly does this?
I know what Gravity is, but how do those numbers influence my actors?
How do you make your numbers up?
Sorry, I am all new to this physics stuff.

I have started out in wrapping all C-Functions into a C++ Interface.
If you want to see some code:
http://code.google.com/p/nightlight2d/source/browse/trunk/NightLightDLL/NLPhysicsWorld.cpp
http://code.google.com/p/nightlight2d/source/browse/trunk/NightLightDLL/NLPhysicsShape.cpp
http://code.google.com/p/nightlight2d/source/browse/trunk/NightLightDLL/NLPhysicsBody.cpp

Now, how do I glue this to my sprite? Just making the matrice from the body and applying it to the vertices?
Where do I set the collision Callbacks?
Sorry to ask but the docs could be really better -.-.
Thanks.