I've used Ionic Framework[0], which is basically Cordova + Angular = Mobile Development. If you know Angular, it's a really good place to start, along with ngCordova[1].
If you don't know Angular, then straight Cordova isn't so bad. I actually did some Google Glass development that way. There are Cordova plugins for just about every mobile function you can imagine, with varying degrees of quality. To learn them, I basically took sample projects and examined them, made a few changes, and checks to see what broke.
If you know C#, you can also look at Xamarin[2]. I don't have any experience with it, though.
Edit: formatting