Noel Chenier, photographer and instructor, has created apps that are worth checking out providing photography ideas and information. They also allow you to get information on various techniques and types of photography. Along with each type there are several photos and tips to go along with them. You can choose a particular category or have the app randomly select one. He has created apps for use with DSLR cameras as well as one that is designed for those taking pictures with an iPhone.
Below is a link to the free version of the Photography Assignment Generator app.