I'm torn on this one. Microsoft recently added a free tool for Power Point that basically functions like those expensive clicker sets that were all the rage a while back. The tool, Mouse Mischief, allows teachers to embed interactive quizzes into their presentations, theoretically making students more active participants in the learning process. The tool also allows teachers to build in quick checks for understanding.
You can access the eSchool News article here.
Since I'm torn on PP presentations, anyway--not very many people do them well (including me, I might add), and they tend to lead to rather deadly lists of points, as this recent article on their use in the military points out, and this classic blog post from Creating Passionate Users.
It could be interesting for simple gaming and reviews, especially for elementary-age students, but the types of responses it allows--yes/no, multiple choice--are definitely NOT the kinds of questions older students should be spending much time on. So, possibly useful for introductory stages, but not much beyond that?
Or, as I said, on those rare occasions when we have to resort to PP lectures, a good way to monitor students' attention!
UPDATE: Unfortunately, this only works with Windows. No Mac version. Grrrrr.....