As a runner I love to keep track of my mileage and speed. The Nike Plus application is the best option I've used so far. It tells you everything you need to know on your run and cheers you on with all sorts of trophies! I had the silver trophy for running more than 25miles in May :)
There is a coach program which is really great. Right now I'm training for a 5K, it's an eight week program with many different types of runs (long runs, speeding up on the last mile, fartleks). The coach program can be too intense for beginning runners with not enough time to recover from one run to another so I'll recommend being very careful with overtraining which can lead to injuries.
The app offers to connect with your friends who are using it and you can also set up your own challenges. It's very easy to use and you can keep your phone in your hand while running.