Alexa Site Thumbnail / Amazon Web Services: This is brilliant. For $0.20, you can access 1,000 thumbnail images of Web sites from an Amazon Web service.
The Alexa Site Thumbnail web service provides developers with programmatic access to thumbnail images for the home pages of web sites. It offers access to Alexa’s large and growing collection of images, gathered from its comprehensive web crawl.
Programmatically grabbing screencaps is something I never figured out how to do. Always wondered. Via Kottke.