On a PC I could move anywhere in a document by using the home, end, shift home, shift arrow, and many other buttons or combination of buttons. With a Mac, they have the lovely feature of making it different in every application. So I always feel like I have to use my mouse to do anything moving around.
There is a great fix for Firefox that I've used in the past, but wasn't working for the new FF3. However, the internet at large has found, tackled, and fixed the problem. If you're on a Mac, and you want your home and end keys to take you to the beginning and end of any sentence, then go here, click, and rejoice.