Powerpoint - Installed on all UAGC computers, Powerpoint is the classic presentation tool. Though lacking in flair, Powerpoints can efficiently display text, images, videos, etc. at the click of a button -- and you can add automatic timers and audio for a slideshow presentation that runs on its own.
Prezi - A more visually-appealing type of Powerpoint. Create a sort of 3-D map of your information and then plan out a virtual tour through it (just go to the site and watch examples to see what I mean). Here's a great example on the Theory of Relativity.
Screen Cast-o-matic - Record videos of your computer screen. No audio available (unless you pay), but you can present audio while you play the video or record the audio separately and try to play both files at once.
TechSmith - Jing - Pretty much the same features as Screen Cast-o-matic.