Stand by Echo Group, possibly best Star Wars themed case mod ever is targeting the power generators. Courtesy of hardware hacker Asphiax, it's a fully functioning battlestation built inside an AT-AT.
Pop open the side of this magnificent mod and there's a fully water cooled mini-ITX PC, with a Core i7 2600K CPU and a Radeon HD6870 inside. Which means it's more than capable of playing SW:TOR, for example and far more interesting than almost anything else to have featured in the Star Wars canon lately.
It even has remote controlled ion cannons on the front.
There's a detailed build diary over on Asphiax's blog, and some more details on this MaximumPC forum post. There's also a video diary
As a child, I could never quite understand the error of scale which only allowed for half a dozen stormtroopers to stand inside the belly of the giant mechanical beast. This is a far better use of space.