I got the inspiration for it from the lifehacker.com feature (which I suspect you've seen) but soon decided that to do it "right" (as I wanted) I'd just have it built from the ground up.
It's on a 4800psi 18" deep slab, fully permitted, fully insulated, finished, the same windows that are in my house were put on, singled to match the house, painted to match the house, steel door, data distribution (ethernet/phone/directv) to 4 points in the office via in-wall distribution panel which also houses a 4 port switch), alarm system tied in, low voltage dimmable track lighting, doorbell wired to chime so I can hear people out front, and heated/air conditioned. Rain gutters are also now on (not pictured) and tied into my yard's site drains.
It's pretty much the ultimate man cave.
Few pics though I'll get some recent ones showing the 32" tv mounted, shelving mounted, blah blah blah.
The pics make it look tiny, but dimensions at 15x10' - ceiling is 10' in the center and 8.5' where it meets each wall, it's downright spacious for one person (in fact most corporate offices I've had were in the 10x12' range)
The outside pics are during the (extremely messy) construction process, landscaping will be tied in shortly the match the rest of the yard.