I have a document camera that I use for a variety of things in my class. I've used it to project what I'm writing on paper when I had knee surgery and couldn't stand at board, up close images of demonstrations and other items that I want the whole class to see. They are very useful. Some even have microscope attachments to show all kinds of things to your class on the big screen.
Many teachers have document cameras but don't know how to best use them or even how to spec one out if looking to purchase one.
I recently found a great Livebinder on Document Cameras from my PLN on Twitter. This Livebinder has resources and ideas for using a document camera in class, lesson ideas, links on different brands of document cameras and much more.
If you have a document camera, or are looking to purchase one, this site is a must-see.
Document Camera Livebinder: http://www.livebinders.com/play/play_or_edit?id=40696
MimioTeach system - great tools for teachers - IWB, CRS, Doc Camera, and more
Livebinders - organize materials in online binders
Luna Interactive Projection Camera - full featured, multi-function, reasonable price