Last Spring while I was student teaching, I brought my iPad2 into the classroom. Since it was my first experience with an iPad in the classroom, I simply downloaded educational apps and games and allowed students to explore the different games and learning apps I had for them. I didn't revolve a center around the iPad for the students to use because I was unsure of how to do so at the time. I did, though, introduce the computers center activity on my iPad, since most of the activities were placed on our classroom blog.
This school year, I plan on incorporating my iPad into the students' centers for reading and writing. There are TONS of apps that can be used for education, and it often can be ought to choose which are worth the download. Well, I found a LiveBinder created by @nzchrissy TeachingSagittarian that includes a collection of iPad apps that can be used in the classroom. She created tabs for each subject/category and some include subtabs to choose from!