Following Goolge and Yahoo!, MapQuest has released an open API that third-party developers can use to integrate mappingservices into their own web sites. The new "OpenAPI" supports most of what Google and Yahoo!'s APIs do, like push-pin markers and pop-up info boxes, with the addition of route-planning that competing APIs lack. For free users, OpenAPI has a limit of 50,000 maps and geocodes (combined) and 5,000 routes per day (compare to Google's 50,000 and Yahoo!'s no limit). To get an idea of what can be done with the API take a look at the sample mash-up, Mapzierge. You can also check out the OpenAPI developers' blog, and if you come up with something cool you should enter their Developers Challenge.