In some cases it's better to pick out the most important relationships in a table and show them by themselves. Even if you don't need visual aids, you may want to use them to help get your ideas across. 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.