I have been really impressed by iSmoothRun for GPS tracking, it's got a lot of cool features.
I also really like Runner's Log. It does have a GPS tracking feature, but when I first stumbled upon it the app was simply a log. You could track your shoe mileage and keep all kinds of personal notes about your run. (Things like what you ate, if something didn't sit right with you, clothing that irritated you, etc. Stuff you might not want to share on a social network, but could be helpful if you are looking for patterns in your training.)