I have done quite a bit of marathon and 10k training before, using different training plan. I think this app does a very decent job at creating training plans for various levels of running. It goes by time, which according to a lot of literature is better than mileage, and it makes it easier to follow wherever you are. It is simple to understand and use. And it works. You need to be familiar with training speeds, so if you dont, just read a bit before you use the app.
UPfan about MapMyRun Trainer - 5k, 10k, Marathon, Half Marathon Training Plans, v4.0.3