Yahoo! has joined the party providing Web Services APIs ala Amazon, Google, Technorati, Flickr, del.icio.us, et. al. Jeremy Zawodny has a good roundup of Web commentary.
One thing I was going to kvetch about was the fact that they have a usage limited API key, like Google's 1 grand calls per day. This feature makes it tough to build a desktop client to distribute for testing, because any decent number of users would quickly chew up your call allocation. According to Phil Ringanalda though, there's a bit of method in their rate limiting madness. Since it's IP address based, roughly each user get's charged for calls, not the developer. Hackers can distribute away, although you can't be profligate with calls, or you'll cheese of users.
Congrats Yahoo!
P.S. SOAP is passed over again.