AlgoVista

AlgoVista -- The Algorithmic Search Engine. From its home page:

Maybe you have noticed that sometimes it is difficult to search for an algorithm or to find the correct classification of a problem, because you don't know the relevant terminology.
Visual, Enterprise-Ready AlgoVista was designed for exactly this situation. Simply enter a small number of data samples that describe the behavior of the algorithm you are looking for -- or the structure of the combinatorial object you want to classify -- and AlgoVista will search its vast database for the closest match.