One of the best I've seen recently is by blippy, http://blippy.com/ http://blippy.com/ Just very simple animations that make it easy to quickly grasp the conce

One of the best I've seen recently is by blippy, http://blippy.com/ http://blippy.com/ Just very simple animations that make it easy to quickly grasp the concept and answer potential questions about the product (security, privacy etc.)