Taken with a DSLR, processed with Photomatix. ( demo leaves a watermark)
Photoshop also does a great job.
There a quite a few programs out there to do it.
I find bracketing 3 exposures, with the center exposure 2/3 below normal makes the clouds a little more dramatic.
Not everyone likes the look, and it's how a person prefers it. If not over baked, you can achieve a really cool natural look.
Watch for clipping and noise when you do it, especially in the skies...
Great for real estate pictures..
One of my old Cherokee, 3 exposures,
<img src="http://wayalife.com/attachment.php?attachmentid=1223"/>
One of the JK, 4 exposures,
<img src="http://wayalife.com/attachment.php?attachmentid=1224"/>
A local tourist building ( Science North) 3 exposures at night
<img src="http://wayalife.com/attachment.php?attachmentid=1225"/>