Though $4.99, this app allows you to annotate video. For PE teachers, coaches, music teachers, science teachers or anyone else looking to make notes on physical actions
iNaturalist is a web site, and an app, for sharing pictures and observations of plants and animals. Thanks to Richard Byrne at Free Tech for Teachers for posting!
Though an iPhone app, this would also work on an iPad. Star Walk is a very cool app that essentially is a mobile planetarium. Find visible stars and planets overhead and take the classroom outside.