If you are looking for a perfect server for your company or organization, Univention Corporate Server (UCS) could be one of the best so far. UCS is a Debian based Linux for server which comes with a professional web based management console. Like ClearOS does, the UCS provides a complete solution for enterprise. UCS also available for personal use, you can download the Personal Edition for free but its limited to 5 clients only.
The new UCS 3.2-3 includes all errata updates issued for UCS 3.2-0 and comprises the following highlights: the new module Active Directory Connection merges the domain administrated by UCS and an existing Active Directory; the UCS setup wizard has been completely overhauled and now guides users particularly comfortably through the domain configuration of UCS and detects; PHP 5.4.4 has been back-ported to UCS 3.2; the OpenLDAP replication has been improved significantly by tracking changes in the directory service with unique IDs; Linux kernel has been updated to version 3.10.11.
You can download Univention Corporate Server (UCS) ISO from this link.