If you are a fan of student response systems (clickers), you might fall in love with Socrative: http://www.socrative.com.
Socrative is a free web application that turns any laptop, iOS or Android device into a clicker response system. Teachers can build a virtual response room online, create a variety of assessment questions, and then have students respond to questions from any wireless gadget. Socrative will even score the responses and prepare a grade report automagically.
Paired with district laptops or student owned tech devices, we now have access to a simple and useful classroom clicker system, for free.
Check out a demo video: http://www.socrative.com/how-it-works.php