The Unsplash API - No-limits, do-what-you-want API for access to 200K+ HD pics.
Roivenue - A marketing intelligence suite built to maximize marketing ROI through data-driven marketing attribution and data integration.
PublicAPIs - Explore the largest API directory in the galaxy
DropUnited - Chrome extension removes United from your flight search
API List - A collective list of APIs. Build something.
CloudSight - Image recognition API; send an HTTP request with an image, get a description of contents.