ChemDraw for iPad allows you to not only create molecular structures directly on your iPad, but share them just as easily via email or ChemDraw's own Flick-to-Share™ technology that allows you to send structures to anyone else using the app. From chemistry student to chemist, ChemDraw is a great learning app and productivity tool wrapped into one.
Khan Academy is well known in the education world as being a fantastic resource for students to watch videos to learn more about topics covered in class. It's also great for non-students who are just thirst for knowledge and want to study a subject on their own time. And for free. The Khan Academy iPad app is the best way to put learning in your own hands.