I love the Flipboard app as a professional development tool. It's a 'social news magazine' that allows you to follow topics you're interested in a gorgeous format. Bonus: my 10-year-old techie son loves it too and keeps current on all things Apple.
Google Drive. Student and teacher sharing documents: students download a written assessment, complete it, and re-upload to the teacher's account for grading. Teachers could share learning videos or students could upload evidence of learning. Free. One major benefit over other cloud systems: it allows document editing on the iPad.
Socrative is a free web-based student response system (with an app now too). Get instant feedback about what students know about a topic. Eliminates the need for expensive hand-helds. Allows teachers to create quizzes, polls, and exit tickets. Can be used in “real time” by students who each have an iPod Touch/iPad or laptop, or by students rotating through one computer in a classroom center or at home.