Best Use Of Amazon Web Services I've Seen
This is the coolest use of Amazon Web Services I've seen: Type in a phrase, and it will construct an image displaying your text using covers of books, music, videos, etc... . Give it a whirl. Click on a cover for more details on the book to purchase the book, making him a few pennies as well.
As an example, here's dang near every PHP book in existence, constructing the letters "PHP". Click on a title to get more information, reviews, etc... . Very impressive!