The Radicale Project is a complete CalDAV (calendar) and CardDAV (contact) server solution.

Blackfire Profiler automatically instruments your code to gather data about consumed server resources like memory, CPU time, and I/O. But Blackfire Profiler is more than figures; its interactive Callgraphs make it straightforward to find bottlenecks and improve performance. Moreover, profile comparisons let you understand the impact of your changes.

An open source monitoring framework.

Baïkal offers ubiquitous and synchronized access to your calendars and address books over CalDAV and CardDAV. Baïkal implements the current IETF recommendation drafts of these industry standards for centralized calendar and address book collections.

A system for coordinating the activities of users via their mobile phones.

Streeme can serve music to most HTML5 compliant browsers and smartphone handsets using the computer you already own.

Running your own identity server allows you to act as an OpenID Provider. You could run one just for yourself, for a community of users or, if you wish, for the general public.