Which (popular) websites support mashable APIs?

Question

Which popular websites out there support an HTTP based API?

I am looking for content of general public interest (hence, Amazon's RESTful API wouldn't qualify, for example).

Some sites which I am aware of:

• Twitter
• Netflix
• Upcoming
• Google
• eBay

Please note that

• Although not a direct programming question, it will help programmers find some inspiration for new projects
• A similar question has been asked but didn't get many responses probably because it was very specific about being RESTful.

Answer 1

Try Yahoo Pipes for many such examples and mash-ups.

Answer 2

The site (with blog) "Programmable Web" collects sites, apis and howtos to create mash-ups.

You can search by programming language, protocols, wether you want something with JSON or SOAP and so on and check out existing mash-ups.

http://www.programmableweb.com/