Our API directory now includes 945 social APIs. The newest is the SmartBots API. The most popular, in terms of mashups, is the Twitter API. We list [num] Twitter mashups. Below you'll find some more stats from the directory, including the entire list of social APIs.
Gnip's Audience API promises to let brands and marketers glean real-time, in-the-moment data about audiences that convalesce around topics, events, or other users. The idea is to give companies as much information as possible about those with whom they might want to engage.