Do a power search (the sarch bar is usles) and check out th "share your MOD's" thread

Hackng just means modfying your n900, because of the open nature of the device you can modify almost every aspect of it.

You will find the comunity really helpfull as long as you try and find things out for yourself before yo ask questions, and search before posting new theads as there is usualy already one on the subject. And remember to use the thanks in the bottom right of any posts you find helpful