Neddick is part of the Fogcutter suite of tools for building intelligent applications. Neddick provides tools for tagging, ranking, discussing, and discovering various sources of knowledge: Web-links, documents, people, etc. It's over-simplifying a little bit, but think of Neddick as sort of a combination of Reddit, Delicious, and Planet. It also includes a powerful search engine and a recommendations engine, and it lets you categorize, rate, tag, filter, discuss, and discover knowledge in ways that most enterprise search applications can't.
Quoddy is an open source enterprise social network, which shares a common "look and feel" and substantial functionality, with consumer facing social networks like Facebook and Google+, as well as proprietary products from Jive Software and Yammer. It makes up one component of the Fogcutter Suite. It is intended mainly for organizational use and therefore has capabilities which make it uniquely suited to provide the social fabric to support organizational knowledge sharing, knowledge transfer, collaboration, and decision support.
Heceta is part of the Fogcutter suite of tools for building intelligent applications. It is an "enterprise social search" search engine that leverages all of the various bits of information from Neddick, Quoddy, and other source of "social" knowledge to provide better, deeper, and more insightful search results than you can get from simple document content analysis. Intranet searching in organizations is usually very poor, largely because page-rank type algorithms don't work well due to the lack of links between documents. But by supplementing the content analysis with scoring based on tags, social graph connections, activity-stream information, etc., and applying machine-learning / artificial-intelligence techniques, Heceta can do a superior job of locating the knowledge and information a user needs.