You can find yourself spending all your time feeding it and ignoring your audience. You can also find yourself staring into its bulb like a deer at an oncoming car. At any rate, remember that when you put something on an overhead, you are asking people to read and that is tantamount to asking them not to listen. There are times when you want them to think for themselves, to read and digest in silence. These times are perfect for overheads.
Slide Shows Even better than overheads are slides shows.
If you have time, learn to use a presentation package like PowerPoint or Corel Presentation Manager. Both are readily available from the computer labs on campus. You can very quickly make useful outlines of what you want to talk about, sort and resort the slides easily and display them in visually interesting formats with very little effort. With equal ease, you can export these files to the Internet, where anyone can peruse them. You can of course secure them so that only those with password access can read them online, but you will be able to show them to anyone who has a browser and your permission.