Designed for 1st-2nd grade students, Murky Reef combines reading and math skills in the context of exploring a coral reef. This is the free version, though there is a more robust version available for $3.99. Students can review numbers, sight words, and vocabulary. There is some reporting built in.
3DTOAD.com is a library of 3D images that you can rotate and explore. It includes skulls, skeletons, dissections, coral, geology, and even music. These could be great visuals on an Interactive White Board or used on an iPad.
Vernier offers a host of products to support physics instruction, and for $2.99 there is now an app. Students can perform hands-on experiments and collect real-time data through the iPad.
Though this version of the app doesn't have as many features, it's free! With an iPhone or iPad, students can create time lapse recordings so as to improve observational skills, document a laboratory, or create a digital story.
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!