Fellow all-things-spatial obsessed blog Cartography has a review of all the major web mapping applications (Google Maps, Map24, Maporama, Mapquest, MSN Maps, Rand McNally, and Yahoo Maps). Categories reviewed in this 9 part series include: types of searches, map display, data layers, directions and overall use. Overall this is quite a nice review including tables to help make it all that much easier to get the high points.