I use TextPad for all of my school coding needs, and it has the ability to let you number the lines. You can download it from
www.download.com, just search for textpad. It's free to evaluate, and $27 to buy, but there's no real restriction on how long you can evaluate it for.
I've been using the same program daily at work for over half a decade now. If there's a better text editor out there, I haven't tried it. Note, though, that line numbers oddly aren't displayed by default--turn them on under Preferences.