HippoRemote - The first is an iPod/iPad app that works with your Mac (or PC) and allows you to use your iPod as a remote mouse, keyboard, remote control & gamepad. The "lite" version is free, so you can try it out and purchase it later if you find it useful. Personally, I like this app. It can be used with a projector/interactive whiteboard from a distance, which is great if you want to offer support to students without "getting in the way". I have only used it as a mouse and keyboard, but I'm VERY interested in trying out all of the features. However, it does seem a bit "sluggish". More testing is necessary.
Socrative -A clicker/response system that allows students/audiences to respond to questions in real-time. It can be used on any device with a web browser (tablet, smartphone, laptop, iPod, iPad, etc.). Teachers login to their account, or go to t.socrative.com and students go to m.socrative.com . Provide students with the virtual room # xxxx, in order to participate. The room will be different every time, so there's no need to memorize it. The teacher asks a question aloud, and chooses how the students may answer (true/false, multiple choice, short answer, quick quiz, etc.) or can create a quiz beforehand. Student results are visible on the teacher's screen or sent in an email. I tested this out twice, once as a student (answering questions for another teacher), and once I asked questions to a student aloud. I also had them complete a pre-made "quick quiz", as well as a short quiz that I created for them. The results can be emailed, or downloaded. A VERY useful way to gauge student learning in an engaging environment!
Edmodo - This is a Facebook-type Social Networking site, but it's specifically for use in Education. I know of schools that have successfully implemented this, and students use it regularly. I have recently signed up my homeroom class, and am planning on using it for communication purposes. My plan is to expand it for use by all classes by Christmas.