DuckDuckGo Zero-click Info includes topic summaries, categories, disambiguation, official sites, !bang redirects, definitions and more. You can use this API for many things, e.g. define people, places, things, words and concepts; provides direct links to other services (via !bang syntax); list related topics; and gives official sites when available.
Rapleaf's Personlization API provides rich demographic data about email addresses in real-time. You will need an Rapleaf API key in order to use this service. You can get one (for free) here: https://www.rapleaf.com/developers/api_access. With an API key, you will have free, unlimited access to age, gender, and city/state/country data. Additionally, we provide many other premium fields for a small price. Please visit our website or email us at firstname.lastname@example.org to get more info on pricing and our premium fields.
Localstreamer.com is a geolocation system that collects informations by searching facebook statuses and twitter updates. The system offers to the developers some free api to work with features in LBS (Location-Based Services).
Resolve DNS addresses into IP addresses and vice versa. New method: check if a port is opened on a given host.
100% free service including sentiment analysis, content extraction, and language detection. Enjoy!