Best URL APIs easy & free to use?

I'm looking for well-documented and free for commercial use APIs.

By "URL APis" I mean something like:

http://dummyimage.com/600x400/000/fff

It outputs 600x400 px iamge with $000 background and #fff text. Just one link! Simple as that!

All APIs I know of:

Google Charts, Google Maps, Dummyimage.

(I know there are Flickr, Twitter, Facebook etc. APIs, but I'm looking for something else)

I don't have any requirements, just want to create a list of these. Any URL that generat开发者_Python百科es content "on the fly" is welcome!

Any ideas?

• Resizer.co is a simple service for resizing images.

Have a look at the API Directory at ProgrammableWeb. Set the protocol filter to GET, POST, REST, JSON-RPC or SOAP. There is plenty of stuff in there!