Welcome to Maemo. You'll find that reading up an anything you want to install onto your phone is crucial in terms of avoiding bricking your phone.

Being open source, there are a lot of programs that are in a development stage that could mess up your phone if you don't know what you're doing. D-Iivil stated this as well to explain why he declined to provide the link. You might find it more rewarding to read up on the programs before installing them as, at the very least, they will also help you better understand your N900.

This ain't no sissy iphone you got.