TurningPoint ARS/SRS/CRT (new one I discovered - Classroom Response Technology), uses PowerPoint 2003/2007 to display questions, answers and responses as well as run the session. If you want to add a bit more competition in to the mix there are the team and individual leader boards and the new wager slide.
What you can also do is replicate game show styles - Jeopardy, Who Wants to be a Millionaire, and even the Price is Right - and adapt them to your learning area. Again it is a way of engaging your students and making learning more about participation rather than just listening.
For a range of game templates here is a great source
Adapt these for use with TurningPoint and the subject you are teaching and add a little fun factor to your formative assessment.