Horde

http://www.horde.org/

PHP based framework.

This project make base for many and many other projects. Widely used webmail program IMP to the contact manager Turba, the calendar manager Kronolith, and many others application based on this framework.

The guiding principles of the Horde Project are to create solid standards-based applications using intelligent object oriented design that, wherever possible, are designed to run on a wide range of platforms and backends.
There is great emphasis on making Horde as friendly to non-English speakers as possible. The Horde Framework currently supports many localization features such as unicode and right-to-left text and generous users have contributed many translations for the framework and applications.