I'm really impressed with BG Hero. We take a look at these stats sites pretty often, but I have never seen a site targeted strictly at PvP data like this one, and with such a clean and interesting view. Unfortunately, it's still getting off the ground, so we're probably going to give the server a run for its money with this link, but give it a few days and head back there when they've smoothed things out.
It'll track your plays and wins in each BG, obviously, but you can also get a whole bunch of graphs and numbers about how you're doing each time you play, including HKs per BG, and killing blows per battleground that you play. The app also tracks your totals daily and weekly, so if you get your character in there and let it update over a period of time, you can see just how you're doing. Pretty amazing stuff if you've been playing a lot of battlegrounds lately (and with the extra XP in there, why wouldn't you?). We're told the site is still being worked on, so expect more updates soon (and Phood is keeping info flowing on his blog), but in the meantime, it looks like a great way to look at your BG progress in more detail.