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.
Blekko is a search engine which uses both algorithms and human interaction for producing high quality search results. Currently serving more than 3 billion pages, Blekko sorts through spam, content farms, and sites containing malware in order to offer only real information to the end-user.
The new Google Patent Search API is now available and lets you search over 7 million patents via code. It is part of the AJAX Search API suite of content-specific Google search utilities such as book search, government search, code search and others.