Mobile Apps
friendly for the high school classroom
Study Blue
Picture source: https://lh4.ggpht.com/PV039X49pR3C-Gy9foMeqZ_1xhEpNnsx2e_GFsW6xRGnQzGbsAMCzI7BBFOkjEcaQA=w300
Quiz Up
You can specifically use this in high school for getting the students to quiz each other on a certain topic in the curriculum.
Picture source: http://upload.wikimedia.org/wikipedia/commons/8/85/QuizUp_Logo.png
Wikibot
Picture source: https://www.maczot.com/prodpics/2368_2368_wikibot9_copy.jpg
Google Docs
It can be specifically used in the classroom to complete in class assessments that the whole class can take part in and read on the Interactive White Board while they answer questions and provide feedback. Or it can be used when students go home and can work on an assignment with other classmates on their own time.
Picture source: http://edudemic.com/wp-content/uploads/2012/04/googledocs-tips-379x243.jpg
One Note
Picture source: http://screenshots.en.sftcdn.net/en/scrn/6653000/6653659/microsoft-onenote-2013-06-535x535.png