Yes, I know, this was released two weeks back, but I'm just getting caught up on some post backlog.
After seeing innovation after innovation built on top of Google Maps (the latest being the Seattle Busmonster), I really wondered why they haven't offered an official API. Well, now they do (noticed first via Vasanth).
From the website:
The Google Maps API lets developers embed Google Maps in their own web pages with JavaScript. You can add overlays to the map (including markers and polylines) and display shadowed "info windows" just like Google Maps. The Maps API is a free beta service, available for any web site that is free to consumers. Google retains the right to put advertising on the map in the future. Please see the terms of use for more information.
One interesting note in there: Google retains the right to put advertising on the map in the future. It will be interesting to see what they plan on doing with this. Will Google Adsense support location-specific advertising in the future?