Best Plant Growing App:

The best app for your phone is from Mother Earth News, the When to Plant App, for $1.99.

http://www.motherearthnews.com/when-to-plant-gardening-app.aspx
https://itunes.apple.com/us/app/when-to-plant/id504304351?mt=8

I have it on my iphone.  I trust it more than some of the other apps that are available because it is from Mother Earth News, a trusted source.

Here's a screen shot off the iTunes page:

When To Plant App from Mother Earth News, at the iTunes Store

I like it because you can put in your zip code, and it will figure out your frost dates for you and then tell you what you should plant (from seed or seedlings) in the current month.  It also has a handy reference guide for looking up plants.