As much as I like OS X, the default behavior of the Home & End keys on the keyboard has never made sense to me. Home should send your cursor to the beginning of a line, and End should send it, well, to the end. If you'd like to fix this, grab KeyFixer from Jim Mendenhall. He's made a quick little app that will update your default key bindings and make it so that Home and End now fit into their natural place in the universe.
Of course, if you'd rather not run a random app, Jim has also posted instructions for doing this manually. (If you're into that sort of thing.)