Selling Kindle Sample Chapters

Here's an interesting opportunity the Kindle offers: Stephen Windwalker, author of the forthcoming book entitled The Amazing Amazon Kindle, is selling a 2,200-word excerpt called How to Use the Amazon Kindle for Email and Other Cool Tricks. In fact, the excerpt is currently #4 in the Kindle Store!

Windwalker's book and excerpt are obviously playing to a very captive audience on the Kindle, but it makes you wonder if there are other opportunities where something beyond a traditional sample chapter could be sold online for a modest price ($2.49, in this case).