VoiceThread is an app for creating and sharing content digitally, and since it is a cloud application no software is required. The application is very versatile, and can be used from your computer or mobile device. Voice thread also has a version specifically meant for use as an education tool in a K-12 setting.
Screencast-O-Matic is an application used to record what you are viewing on your screen.You can add audio to the text you are recording on you screen, and then upload the recording to youtube. This could be used in an education setting as an alternative to a traditional assignment.
Poll Everywhere is an application that uses text to poll an audience or classroom and receive the results in real time. This is especially effective in a classroom situation to get students involved in class discussions.
Google Drive is an app that allows online sharing and storing of information. In a classroom setting it can be used as an interactive discussion forum in real time. The storage of information makes this a great tool for students, they can use it in class and then later revisit the information as a study tool.
Animation Creator is an application that combines the drawing app from the iPad with animation technology. This would be an ideal tool to use in an art class setting, it would allow students to take their creations and turn them in to films.