Fllowing are some links to x.org Foundation website, they are useful but hard to find the entry point, so I'll record them here to make the acess more easily.
The page which discussion the module of the X Window:http://www.x.org/wiki/ModuleDescriptions
This page also target to the modules but it just contains name of modules list:http://www.x.org/wiki/ModuleComponentList
Here the page disscuss the version of every modules inside X Window Version 7.1, 7.2, 7.3http://www.x.org/wiki/Releases/ModuleVersions
The workgroup of X Architecutre, which seems intresting to me,http://www.x.org/wiki/ArchitectureWorkingGroup
The other group in X.org Foundation:
And, the Project base on the X window or closely related to X Window,http://www.x.org/wiki/RelatedProjects
Here are the documents, lots of!!! :-)http://www.x.org/wiki/DocBook
And the specificationshttp://www.freedesktop.org/wiki/Specifications
Anything you wana to find on the X.org website, you can search it, it's the quickest way to reach you aim page.