Which Web services are the most bestest ones?

[Clay Shirky]

So someone asked me an obvious but hard to answer question today:
What are the best examples of web services currently running?

They didn't mean frameworks like JXTA, SOAP, UDDI, or Hailstorm, or
implementations for developers to build on top of like idoox, Grand
Central or KnowNow. They meant actual Web services, the thing all this
protocol/developer framework work is supposed to result in.

I could only think of a couple:

moreover
meerkat
juice (sort of)

What else? There must be something useful out there other than
currency converters and Starbuck's locators listed on Xmethods, nu?

-clay