The Cray-1 was the fastest supercomputer in 1976. Today, even the iPad dwarfs its humble 133 megaflops and a fast PC can easily surpass 100 gigaflops. This Cray-1 replica houses two PCs, but it looks as good as the original:

It's a lot smaller, however: 77 inches tall compared to the 25.6 inches of the 1/3rd model. And most of it is empty space, unlike the original, which was packed with 200,000 integrated circuits, 3,400 printed circuit boards, and 60 miles of wire, all liquid cooled with freon. [bit-tech via Engadget]