Little known or useful Web Services we all should know about

Question

Web services and web APIs have managed to increase the accessibility of the information stored and catalogued on the internet. They have also opened up a vast array of enterprise power functionality for smaller thin client applications.

By taping into these services developers can provide functionality that would have taken them months perhaps years to set up. They can combine them into single applications that make life generally easier for its users.

Whether displaying information about the music being played, finding items of interest in the locale of the user or just simply tweeting and blogging from the same application - the possibilities are growing everyday.

I want to know about the most interesting or useful services that are out there, especially ones that most of us may not have heard about yet. Do you maintain an API or service? or do you have a clever mash up that provides even more benefits than the originals?

Answer 1

YQL - Yahoo provide a tool that lets you query many different API's across the web, even for sites that don't provide an API as such.

From the site:

The Yahoo! Query Language is an expressive SQL-like language that lets you query, filter, and join data across Web services.

...

With YQL, developers can access and shape data across the Internet through one simple language, eliminating the need to learn how to call different APIs.

Answer 2

The World Bank API is pretty cool. Google uses it in search results. My favourite implementations are the cartograms at worldmapper.
_{(source: worldmapper.org)}