Let’s start with what an API is. An API stands for Application Programming Interface. It’s a way for computer programmers to use the resources/data of an online resource. There are other ways that programmers can get data from online resources (like screen scraping) but APIs usually make the job easier and give online resources a way to control access, provide specific sets of data/functions/resources, etc.
APIs have been around a long time, but they showed up on my radar in April 2002 when Google released its Web API. Since then Web service APIs have exploded. There must be hundreds of APIs out there for an incredible range of sites.
APIFinder (http://www.apifinder.com/ ), launched at the end of August by JupiterWeb, lists available APIs by several categories, including language and operating system. You can also browse by function (wireless, e-commerce, search, etc.) The site also offers a brief list of API articles .
Browsing the Web APIs category, I found a list that spanned from “24-hour Accurate Business and Government Lookup” to “YouTube”. The list defaults to alphabetical organization but can also be sorted by date of addition or provider (man, Yahoo has a TON of APIs.) The browse list has a description for each API (which varies in its usefulness) but clicking on the name of the API gives you a detail page that’s a little more useful, providing information on whether the API costs money or not (many of them do), functions, languages/OS, and the interface to the data (most of the ones I looked at were SOAP and REST with one offering XML-RPC). There’s also a link to download the API (takes you to the Web page for the API) and a link to e-mail the contributor.
A lot of information here but you’ll need to be a bit on the geeky side to get the most of it. There is an APIFinder FAQ but a little information could be added — pointers to very very basic API articles, a glossary (“What’s SOAP? What’s REST?”) etc.