CentOS 6
From Oxxus Wiki
With its latest release, CentOS, which derives its name from Community ENTerprise Operating System, developers provided many, long awaited improvements of Operation System features. Upstream compatibility with RedHat, EL6 is intended, although CentOS is OpenSource, while RedHat EL is gone to commercial releases.
There are many improvements and changes from the last release. New Linux kernel is introduced, and with version 2.6.32, many issues related to device drivers are now sorted out so there is no need for custom kerenels implementation. Kernel from distribution is one of the latest, stable, releases. New kernel offers feature named “tickless” which improves laptop batteries life time as its power aware kernel, saves power.
Another improvement, related to disk system improvement, is introduced, with EXT4 file system support, which however is optionally offered to user to chose within OS installation process. Default file system is still EXT3. Web server improved version,[1], version 2.2.15 along with PHP, version 5.3.2 is now available by default which provides faster, and more stable web services.
New version of MySql, version 5.1.47, and PostGreSQL, version 8.4.4, are now included with latest release and offers reliable database engine. These are the most important features that are improved over last version but for detailed features offered with CentOS v.6.0 please take a look at official pages.