For developers using Solaris operating system and coding in Java the Bloomberg API offers this library. Solaris users should be aware that the Solaris libraries can only be used with the Bloomberg Server API and B-Pipe data feed products and are not compatible with the Desktop API. The Bloomberg API provides free, unrestricted access to raw financial data on current market trades (either real-time or delayed), reference data on historical information, and records of intraday trading. As part of their Open Market Data Initiative the library is offered under a "free-use" license, which allows unrestricted access of the interface's header files, documentation, and programming examples.
At some point before long mashups will start becoming more utilitarian and less one-off novelties. Currently one of the more useful utilities built on web APIs is the blueorganizer Firefox extension from adaptiveblue (a ProgrammableWeb sponsor).
Innovation in web service APIs is not always technical, sometimes it's about money. Such is the case with Yahoo's announcement that later this year they will begin charging for usage of BOSS (Build your Own Search Service), their search web service for developers. Given that search revenue is typically ad-driven, and that advertising doesn't typically mesh with APIs, this has meant that search APIs have been one of the most challenging classes of APIs for providers to monetize. So it's notable to see how Yahoo has chosen to tackle this: via a 'utility' pricing model, somewhat akin to how infrastructure services like Amazon Web Services charge by usage.