Post-it Plus is a new iPad app from the makers of the original Post-it Notes. With this free app installed on your iPad you can snap a picture of a collection of physical sticky notes and have them quickly digitized. Once your notes are digitized you can re-arrange them, share them with collaborators, or send them to another application like Dropbox. If you have multiple sets of notes you can combine the best notes into one board through the Post-it Plus iPad app. Watch the video below for a short overview of the app.
Post-it Plus does require you to have updated to iOS 8. If you and your students have done that, then Post-it Plus could be a good app for digitizing the output of a brainstorming session that started with physical notes.