I'm not sure exactly what sort of information you're looking for (Developer data? Compatibility issues? Graphics engine evaluation? et cetera), but I'll throw some information at you.
http://www.devmaster.net/engines/
This provides a lot of development information about graphics engine development. It touches on areas like the capabilities of the major graphics APIs (OpenGL and DirectX), the limitations of various development platforms, and methodology for development using various engines.
http://cg.cs.tu-berlin.de/~ki/engines.html
This is essentially an orgy of (somewhat biased) evaluations of various 3D graphics engines. Much of the information on the site is summarized and abbreviated, but links are provided to websites devoted to the particular engines where more information can be found. It's somewhat better organized than the last link, even if the site design is somewhat fugly.
http://www.technomagi.com/links/graphics.html
This is for armchair game designers, basically. It provides amateur tutorials, evaluations, and howtos. Keep in mind that in this case "amateur" also applies to the fact that some of what is here might contribute to forming bad habits with game design. On the other hand, there's a lot of information there.
http://www.filename.info/f/dxdiag.exe.html
This is sort of a quick breakdown of what dxdiag is. It's probably not what you're looking for, but this is a very useful site for figuring out what a given file does, so I thought I'd throw it in here anyway.
http://support.microsoft.com/?scid=kb;en-us;q190900
Speaking of the DirectX diagnostic tool, this is the official Microsoft description of it.
(to be continued, due to character limits)