This independently constructed answer library written in C# is made for .Net applications to interface with the DuckDuckGo Zero Search API. Though not officially supported by DuckDuckGo, the library is listed on the DuckDuckGo API documentation under supporting library integrations. DuckDuckGo is a search engine which distinguishes itself by not tracking its users or generating results based on its user's previous behavior. The DuckDuckGo Instant Answer API provides free programmatic access to many of the search engine's instant answers, pulled from over 100 independent sources.
It looked like Yahoo BOSS was dead 18 months ago, when the Microsoft search deal was announced. Behind the scenes, Yahoo has been re-tooling its Yahoo BOSS API, which lets developers Build their Own Search Service. With a re-launch coming next month, it has released technical documentation, which includes changes to authentication, the option to use ads from the service, as well as introductory prices for the service.
SEOmoz recently provided an API to their search engine optimization service, and inevitably comparisons were made to Site Explorer, which is a similar service offered by Yahoo. In a field where stats are king, the 500 links offered by the free SEOmoz service seemed to come up short against the 1000 links offered by Site Explorer. That has now changed, with SEOmoz doubling their volume of data available with their free API.