Often times it seems like the APIs that get the most attention are those you can use to produce visual things: mashups, Ajax effects, etc. Not that there's anything wrong with YUI, Flickr, or Maps, of course, but there's a class of APIs that's a bit more behind the scenes and all about getting down to business.
Our friends in Yahoo! Search Marketing (we call 'em YSM for short) just announced their new technology solutions center which includes access to the advertising APIs used for campaign management:
...today we?e released a new Technology Solutions section that allows Yahoo! Search Marketing Advertisers to apply for API access provided through our Enterprise Web Services (EWS). EWS enables you to develop software that interacts directly with Yahoo! Search Marketing campaign management systems.
So if you're a developer in the Search Marking world and have been hoping to start playing with Panama, head on over and check it out.
Yahoo! Developer Network