High Dynamic Range photography is a really cool technique to aggregate pictures with various exposure into one stunning picture. There is now a free online-tool to do this at yohdr.com. I tried it out - it's great!
There is only one catch: The three pictures must (obviously) be identical, except exposure. The picture I used had some branches that moved in the wind, and on the final picture they were not aligned. Still, for stills, this is pretty amazing.