Tao Presentations seems to be the answer, they support 3D both with glasses and without glasses. The free version put a color watermark on the top left (think about your average TV network logo). But please, please, read Death by Powerpoint before you do anything. Engaging presenter with plain blackboard is better than boring presenter using whatever latest tech.
EDIT : I just tried putting stuff into it. Personally I like SmartArt features in Office 2007 and above better to visualize concepts and points than the simplistic feature in Tao. Also, will these viewers of yours be comfortable in viewing the 3D display? My experiences with 3D display watching 3D music videos /playing 3D games are usually few minutes of wow followed by watery eyes for hours.