We're getting used to this kind of info out of Gigapan. Recently, photographer Gerald Donovan took the GigaPan Epic Pro robotic camera mount, equipped it with his Canon 7D and let it start snapping for more than three-and-a-half hours. Ultimately, he ended up with more than 4,250 frames, which combined into an image with a resolution equal to 44,800-megapixels. According to the press release, the image would be bigger than 1,200 billboards if printed out.
Donovan goes out of his way to explain on his page that the image was taken as a technical experiment and wasn't meant to be artistic. But, the odd cast effect given off by the poor air quality in Dubai and the interesting focal effect achieved by stitching together more than four thousand images makes it very interesting to view none the less.
His camera was equipped with a Canon 100-400mm f/4-f/5.6L. The shots were captured at 400mm and by the time he was done shooting, all of his gear was hot to the touch.
Clicking around the image itself is extremely interesting, but beware that it will take up a fair bit of your computer's resources to render it smoothly. That doesn't seem so bad, though, when you consider the fact that Donovan had to go out and buy new parts for his already fast (Core i7, 12 GB RAM) computer just to render it.