Koraa/Avatar?

Lots of people seem to like this "Legend of Korra" show, and I've heard the helpful tip that it's viewable free on the Nickelodeon website. But... um... turns out I haven't managed to watch Avatar yet. How important or helpful would it be to see The Last Airbender before leaping into this newer show? Is there anyplace I can conveniently watch that? (And ideally at no extra cost to me. Netflix is a viable option, particularly if it's streaming.) I have no idea when or if I'm going to get to either one, mind you, but I'm interested in adding them to my queue.