BuiltWith

BuiltWith provides technology and SEO profiles for any site on the Internet. The service provides the server, analytics, advertising, JavaScript libraries, programming language/framework and other technical information. Further, the SEO profile shows top keywords and phrases. The BuildWith API provides programmatic access to BuiltWith's data. Free accounts must provide attribution, but paid accounts (starting at $9 per month or $99 per year for 500 lookups) can use the data without attribution.