If you use a projector in class, you probably have piles of powerpoint presentations. Why not let your students look at them at their leisure (and you can keep a copy online in case you lose the original). You can make a set of slides from a powerpoint presentation in minutes, upload it to SlideShare and share it publicly or privately.
You can add your voice to the slides if you like. This is a wonderful way to share your information with your students.