Hi,
I want to learn to program on a MAC (using Xcode) especially using the iSght webcam. Does anyone knows some good tutorials, soure codes or help me any further ...?
Are you already an experienced programmer? If you're just getting started learning to program, have a look at the guides at the top of the programming forum, also do a search using the link in my signature for topics on learning to program on the Mac (there are TONS of threads on this topic already).
You can tap into the iSight, but that is relatively advanced, and you likely won't reach the point where you're writing software that interacts with it for a good while, if you're just learning how to program.
If you're already an experienced programmer, please forgive my assumption to the contrary.