Sortuv is a search engine that allows you to "start with something you like, and discover more." Music, stores, restaurants, hotels - begin by searching with something you like (eg. The Decemberists) and it will create a visual data map of other items/places (eg. bands) you might be interested in based on relevancy.
It is still in BETA form, but I am already finding it promising for finding restaurants in NYC that are similar to restaurants I like in, say, Chicago or San Francisco - Sweet!