The way to accomplish this effect is to use what's called the "Auto Exposure Bracketing" feature of a camera, which in sequence takes an under-, properly-, and over- exposed image. In post processing, software seams together the three exposures into one image.
Specifically, the darkest areas of the overexposed photo (which brings out the detail in the dark portions of the photo) are blended with the brightest areas of the underexposed photo (which preserves the detail of the bright areas), while the properly exposed photo's midtones are preserved.
The effect is like a supernatural flash, but without using flash... which has issues of adding false color, casting unnatural shadows, and illuminating closer things more than farther things.
My contribution to the blogosphere for today is an HDR image of three shots I took back in June at the Sagrada Familia in Barcelona. It's what I'd call a "neo-gothic" cathedral (begun in 1882, and still under construction), with very cool stained glass windows.