KindleGraph is the work of a developer by the name of Evan Jacobs, a former Amazon programmer. He built the service a couple months ago as part of the DocuSign hackathon, but it managed to have slipped under my radar until now.
The service is fairly straightforward.You can visit the site, choose a book or author you like, and then request an autograph. Unlike Autography, Kindlegraph doesn't make a signed ebook. Instead, it offers authors the option of signing and sending a note to their fans.
Here's a demo video that Evan posted which explains how it works:
I'd like to see more personalization options (real handwriting would be good), but for a free service this is actually pretty nice. Also, it's pretty closely tied to the Kindle. Authors can only sign up by entering their book's ASIN (Amazon's product code).