The main ideas which you wrote on the top lines of the 3x5 cards can easily be made into a bulleted list on a slide, poster, or foil. If you do this, you have to get the timing right before you make your visuals. This is a particularly good application for progressive disclosure, which is described below. Overhead foils are the most effective visual medium for classroom-size areas. For larger rooms, you may want to use slides.
Visual aids are most effective if they display only a single idea each.
On each foil, put one key phrase, a single line from a table, or a line drawing illustrating a single point. A simple, pointed visual aid focuses attention on that point. A crowded, jumbled visual aid not only conveys no information, it distracts your audience. An effective technique for use with visual aids is progressive disclosure. If you put a list of three things on a foil, the audience will read all three, anticipate what you will say, and begin thinking of other things.