PUBLIC MARKS with tags collaborative & demo

Has two webapps: SMBWorks - Tool for collaboration, information sharing, document management, project management and extranet administration for all users. SMBApps - Enhanced, department-specific applications for sales, marketing, customer support, HR and finance, fully integrated and targeted for functional users.

It's an open source server and client system for enterprise messaging and collaboration email, contacts, and group calendaring. It has open APIs and a lot of potential for mashups. I was very impressed, desktop type interface with filders and tags.