XigniteGlobalQuotes

This API offers delayed stock quotes for equities trading on more than 50 international exchanges. In addition to stock quote (bid/ask) data, the market data feed also provides intraday tick data, volume and time weighted average prices and other stock market data statistics including open, high, low, close, and other data for more than 150,000 global active equities, depository receipts and ETFs.
XigniteGlobalQuotes

identi.ca

Use the identi.ca API to include Identi.ca either as an option in your programs or as the main platform for development. The Identi.ca API supports an API compatible with Twitter's, based on the open source project StatusNet. Identi.ca users can post small (140 chars or less) text notices and also subscribe to others' posts. Also, Identi.ca now supports a full feed of the public timeline via XMPP, which is likely most useful for data aggregators. Identi.ca is different from Twitter, Jaiku, Pownce, Plurk, and others because it is open, transparent, built on free software, and all the data is openly available via the Creative Commons Attribution license.
identi.ca

Echo Nest

Use the Echo Nest APIs to perform actions related to music. Using the APIs, you can tap into the Echo Nest capabilities related to music search, music information, music recommendations, and remix tools. Also, use machine listening features including beat and pitch. Get feeds for any artist, analytics, or remix. Get song analytics that include fade in, fade out, beats, bars, duration, key, loudness, tatums, tempo, metadata, mode, and sections. Get artist news, profiles, videos, audio, URLs, and blogs. Get which artists or songs are at the top of the charts. Use the Echo Nest Remix API to alter music and video from the web.
Echo Nest

Yammer

Yammer is a private social network for companies. The tool was originally for making companies and organizations more productive through the exchange of short frequent answers to one simple question: "What are you working on?" The Yammer API allows third-party developers to create their own Yammer applications.
Yammer

Directed Edge

Use the Directed Edge API to locate connections among a collection of items. With Directed Edge, you can help your users find interesting information, good music, cool people, and exciting events. If you run an online store, Directed Edge has a recommendation engine that can help you sell more products. If you have an information site, Directed Edge can help make navigation easier. Use the API to get a dump of all items in the database, including links and tags for each item. Or get 20 related items, sorted by relevance.
Directed Edge

Social Actions

Use the Social Actions Open API to search the SocialActions.com database of volunteer and philanthropy opportunities, called social actions, useful for those interested in peer-to-peer social change. The database aggregates the opportunities of over 20 organizations, and the results include the title, description, location, action type, and source URL of the opportunity. Some of the organizations that are aggregated are Democracy in Action, MicroGiving, VolunteerMatch, and Helpalot. You can narrow your request by any of the following action types: Group Fundraiser, Campaign, Pledged action, Event, Affinity group, Volunteer, Micro-credit loan, or Petition.
Social Actions

RentRent

Use the RentRent API to return the rentals listed on Craigslist. You can search for rooms, apartments, or houses, and you can provide a parameter so that you only return rooms, versus apartments and houses. Also, you can provide parameters for min and max latitude and longitude, number of bedrooms, and number of bathrooms. You might integrate the data with Google Maps, Yahoo Maps, or Virtual Earth. Rentrent is not associated with Craiglist.org.
RentRent

Wikipedia

The unofficial Wikipedia API. Because Wikipedia is built using MediaWiki, which in turn supports an API, Wikipedia does as well. This provides developers code-level access to the entire Wikipedia reference. The goal of this API is to provide direct, high-level access to the data contained in the MediaWiki databases. Client programs can use the API to login, get data, and post changes. The API supports thin web-based JavaScript clients, such as Navigation popups or LiveRC, end-user applications (such as vandal fighter), and can be accessed by another web site (tool server's utilities). The API uses RESTful calls and supports a wide variety of formats including XML, JSON, PHP, YAML and others.
Wikipedia

Authentic Jobs

The Authentic Jobs API allows you to build a jobs mashup. Use the API to list jobs, list locations of jobs, job types, jobs at certain companies, and so on. Get results returned back according to Freelance-only or Full time jobs. Authentic Jobs specializes in hooking up standards-aware designers and developers with companies seeking to hire them. You can filter the results to show only Designer jobs or only Developer jobs.
Authentic Jobs

urlBorg

Use the urlBorg API to shorten URLs, get a history of the short links you created as well as a click history of the ones you and your friends clicked, get stats, lists, and export data. Visit the main urlborg.com site to view a page about how urlBorg is different from other URL shortening services.
urlBorg