Yahoo's getting in the game. REST based APIs for Search, Images, News, etc.
Paul Bausch, a creator of this fine blogging service (blogger), and author of Amazon Hacks, has a quick Yahoo API sample up on O'Reilly site.
BTW, if you want to get started with the Overture APIs, they are there, you just have to look carefully. Unfortunately, you need to process DTC-XML for Overture. So once people learn SOAP, REST and REST / DTC-XML, we can expect some cool apps!