I think one of the easiest things I've seen teachers do in elementary level is to use it to share science and social studies images and videos! For example, talking about an elephant and showing a book to a kindergärtner is wonderful; however, showing them a video of an elephant on encarta online or hearing an elephant sound off....it's brings it alive and doesn't take that much time!
I have used a program on-line called the Monster Exchange Project with my second graders. They loved it. They use their writing skills to describe how to draw the monster they create and then we work with a partner school on-line to exchange our work. They then have to draw the monster using my students description. Their art works are then placed side by side on the site to view. It is a great writing, reading and drawing lesson. The on-line address in www. monsterexchange.org.
Hope you try it!
Donna