Glamor is a 2D rendering acceleration implementation that's based upon OpenGL. The three parts of Glamor for X.Org are: a 2D rendering acceleration implementation, integration of Glamor into Xephyr, and a stand-alone DDX driver. The standalone Glamor driver uses this 2D rendering acceleration over OpenGL while leveraging KMS and EGL with Mesa.
While many are still interested in Xephyr, the Glamor DDX is interesting as it allows another generic (hardware-independent) X.Org driver that accelerates 2D using the 3D engine via the EGL interface with Mesa and without any native window system. As long as the graphics hardware has Mesa support and complies with the Linux kernel mode-setting (KMS) interfaces, it should work.
Current limitations though are not full GLX support, DRI2 support still isn't fully complete, and currently only Intel graphics hardware is supported. Intel support is only there due to the KMS, Mesa/EGL, and GBM requirements.
Glamor has been in development for a long time, but up to now it's not been heard much outside of its small development group. Glamor consists of more than 10,000 lines of new X code spread over 200 commits. Among the well known X.Org developers who have worked on Glamor include Eric Anholt and Kristian Høgsberg.
The Glamor DDX is faintly similar to the Xorg/XA state tracker that allows 2D acceleration via the GPU's 3D engine in a fairly generic manner. Both depend upon kernel mode-setting support, but Glamor also depends upon EGL support while the Xorg/XA state tracker targets the Gallium3D hardware drivers. The Gallium3D state trackers for X.Org are also independent of any specific xorg-server changes.
See more in the Glamor pull request announcement. Glamor has already been criticized due to little public review prior to its pull request and not being well known within the community, but it's largely independent of the rest of X.Org and its developers hope the code will now be examined by some new eyes.