Have you heard about Google Maps? It's a very innovative way to see and browse maps which is a lot different than how other map sites (MapQuest, MapsOnUs, MapPoint) do. The most interesting part is the map that is shown to you always fits in your browser window and is made up of tiles. You can drag with mouse on the map to pan it in all four directions. Everytime you pan, the unshown tiles are downloaded and shown to you. All the tiles at each resolution are fixed. So if you use a map of a small area over and over again most of the tiles won't even need to be downloaded as they are already cached by your web browser. This reduces the network traffic and improves the user experience.
This map site is still in beta and I'm expecting many more things like searching based on a local area (which is partially available but not very powerful yet). Imagine if you are looking to buy a new house and you know which geographical area you want to search the houses in (not by zip code or city name but by map), then a tool like google maps can offer a visual aid in your search by showing current available homes for sale with your search criteria on the map! I know this kind of feature is not available yet, but there is huge potential here and I hope google folks are smart enough to figure out a business model around it...