This website, called Protractor, is specific to using a protractor for the study of angles within your geometry curriculum. It is simple enough and visually appropriate for even showing right angles to kindergartners or first-graders. It is so complete and is shown full screen without any distractions, that I was extremely impressed with it. This would be perfect to be shown on an Interactive White Board.
I found it on Teacher First, an excellent newsletter that is in my in-box every Sunday morning, just like the New York Times (but that arrives in my mailbox!) Sign up HERE to get Teachers First sent to you.