Class Dojo is a classroom management tool that my brother told me about last week. I have used it with my upper elementary classes and it has helped quite a bit. ClassDojo is a free web based program where a teacher uploads a class list and can give real time feedback to his students (Both positive and negative).
Using the system is easy, all you need to do is click on a students name and give them an award.
It is a points based system and each student can see if they are currently in the Green(positive points) or in the Red(negative points).
When a student receives a positive award their name will appear on the screen for a few seconds.
I usually project the page on a wall and control the program from anywhere, in the gym, with a wireless mouse.
I really like how you can see a graph of the different types of comments you gave out during a class. That way you can see your ratio of positive and negative comments.