I remember seeing the Great Bear in the Tate Modern, which was basically a map of the tube, but on closer inspection, you could see that the stations had names of famous people, and each line had a different theme such as "Scientists" or "Philosophers". Well, this here is a great site which has other variations on the map. Some of them are really funny, such as the food one! Pimlico = Pimms and Marble Arch = Marble Cake... genius!

And here's one which has various bands and musicians of today, with musicians who belong to different genres at stations with interchanges. And then there are more practical ones such as the a map of the actual physical locations of the stations themselves.