There are many education related apps. Find one free app and one app that you have to pay for that would be beneficial to a classroom.
Here are two apps that I love.
This is the best lesson plan book I have ever used. I hate making lesson plans but when you have 13 elementary preps and 10 high school preps a week you have to have something to keep your head together! You can use the program on line and on the iPad but only use it on the iPad. You can email a weeks worth of lesson plans. Love this because my elm principal wants lesson plans the week before you teach them. My students also think it is very cool that my plan book is on my iPad.
McGraw Hill Free
This link has all of the McGraw Hill app. I do not use them in my classroom but my kids use them at home. They also use them at my daughters school. It is nice that they have a fun way to practice math at home and my daughter is able to work ahead and my son is getting a head start. (I guess it is homeschooling and that is education). I just noticed that they have flash cards for music. I have not seen them before so I am going to check them out. My daughter may use them too because she takes piano lessons.