Every now and again when you study up on a place with your favorite mapping website you probably wonder..."What does it look like in OpenStreetMap?" The BBBike/Geofabrik allows you to explore the same geography via eight different map layers from 16 different source at one time. Among the choices are a host of OSM layers, Esri, Yahoo, Google, Bing and a few I've not heard of!

http://tile.bbbike.org/mc/