Current release
The latest release of X.Org was X11R7.6, on December 20, 2010. Of note, this release added xorg.conf.d directories, InputClass configuration sections, udev support on Linux, improved documentation, and integrated xcb. Read more in the Release Notes.
Download: mirrors, master site.
General
Individual releases of Xorg modules are here.
6.8.0 post-partum: lessons learned.
For module maintainers: HOWTO Make a release.
Old releases
X11R7.5 (Released: 2009-10-26) Release Notes. Of note, this release added Multi-Pointer X (MPX), RandR 1.3, E-EDID support and DRI2.
Download: mirrors, master site.
X11R7.4 (Released: 2008-09-23) Release Notes
Download: mirrors, master site.
X11R7.3 (Released: 2007-09-06) Release Notes Of note, this release added RandR 1.2 and input hotplug support.
Download: mirrors, master site.
X11R7.2 (Released: 2007-02-15) Of note, this release added autoconfiguration support, and enhanced support for GL-based compositing managers, such as Compiz and Beryl.
Download: mirrors, master site.
X11R7.1 (Released: 2006-05-22) Release Notes
Download: mirrors, master site.
X11R7.0 (Released: 2005-12-21)
Download: mirrors, master site.
For more complete information, including a release history, please see the historical releases page.