Along the lines of What should I read next? Literature map is a nifty site that can give you some insight into what other authors you might enjoy. Instead of giving you a list of books you may enjoy, it displays a web of authors (Thinkmap's Visual Thesaurus is a very good example of the way the data points are represented). Those authors that are closest to the one you entered are the ones, according to this, you are most likely to enjoy reading.
I ran this through a couple of test runs, and by and large, the results seem to be pretty relevant. Take, for example, what the service returns when you enter Don Delillo. The number of names returned, compared to some of the other authors I tried, is a bit low, but that makes it easier to talk about. For instance, some of the closest writers to Delillo are Thomas Pynchon, David Foster Wallace, Fyodor Dostoevsky, and Umberto Eco--sounds about right to me, though the Dostoevsky may be a bit of a reach.
Once you get to the outer reaches of the web, however, it starts to break down. (Tom Robbins? Hello?) I have a feeling that a lot of these writers on the outer reaches would show up for just about any literary author I choose to investigate. In any case, it's something cool to play around with if you have a bit of time to kill.
NP: "Essex Dogs" - Blur