Back when we had opaque projectors, we were happy to just project a book page, a picture, etc. Now the quality is so much better than you can super-educate with it. Some examples:
Using a pencil or pen point to focus attention on a precise part of an image or passage
Writing on a copy of a student paper as the class suggests comments for improvement.
Using pre-word processed mini-pieces of paper to add higher-level questions or comments to the shown item. Just put the piece of paper above or below the image or passage to be projected.
Using a sheet of paper to reveal line after line as the students read it. A teacher can do focused comprehension questions or improve speed reading.
Having a student draw what you are saying.
How else do you super-educate your use of an document camera or Elmo?
© Harry Grover Tuttle, 2007