Not an entire website that I'm aware of, but a quick summary of the process that the late Mr. Jeffries went through to design the TOS Enterprise can be found
here. Not only will you see the sketch that inspired DD's Glamorgan, but also ones that inspired the Daedalus design, the "Enterprise" series Vulcan "ring" ships, and even some that have a certain similarity to the Defiant (though I don't know that the people who designed the Defiant actually used them as any sort of inspiration). You can also find a similar summary on the design of the Galileo shutlecarft
here. It's safe to say that Star Trek would look very different without Matt Jeffries...
Those interested in Trek concept art in general should check out the main site at
Starship Datalink--there's several articles in the "Concept Art" section (taken from the Star Trek Magazine, mostly) about how various ships were designed.