Check out this interactive Literature Map - the tourist map of literature. You key in an author name and it shows other authors you might like, or that are similar. You can click on any of those names and keep going. Very fun. I find associative lists endlessly fascinating, since they are reflections of how we classify things -- there's more than just alpha order or LC or Dewey, as we know, so I love looking at other systems of relationships.
It is part of a Literature Site called Gnooks, which has an author recommendation engine too. You type in the names of three authors you like. I typed in Garrison Keillor, Lorna Landvik, and Elizabeth George, and it recommended Jon Hassler. A good recommendation, except I've already read all his books!
Gnooks in turn is part of Gnod, an AI project developed by Marek Gibney. Here's what Gibney says about Gnod:
Gnod is my experiment in the field of artificial intelligence. Its a self-adapting system, living on this server and 'talking' to everyone who comes along. Gnods intention is to learn about the outer world and to learn 'understanding' its visitors. This enables gnod to share all its wisdom with you in an intuitive and efficient way. You might call it a search-engine to find things you don't know about.
Gnod has recommendation engines for music, books, movies, and people.
(Note: I cross-posted this to Sub 2.0.)