Dan Burns gave a demo of the Renaissance clickers he uses at Los Gatos HS.
Paul Robinson has adopted Qwizdom clickers at San Mateo HS.
I have adopted iClickers at Rio Americano HS.
We also had an extensive demo of Interactive Physics by Paul Mitiguy. Because otherwise, we wouldn't have covered mechanics (again)!
Lastly, if you have a Mac and want to make appealing and engaging presentations that won't look like presentations students have to sit through in their other classes, I highly recommend the use of Apple's Keynote, part of the iWork productivity suite.