The Nobel Prize website was offline at the time of writing presumably unable to take the strain of hacks and bloggers every scrabbling to learn of the winners. Anyway, Mario R. Capecchi (US) and Oliver Smithies (US) and Martin J. Evans (UK) have won the 2007 Nobel Prize in medicine or physiology for their work on gene targeting in mice.
Their research is being used to help scientists understand at the cellular level why certain diseases, such as cystic fibrosis, occur and why otherwise healthy people can succumb to cardiovascular and neurodegenerative diseases, diabetes, and cancer.
The same threesome the Lasker prize in 2001, so in the absence of a Nobel website you can read more about the award-winning work here. Thanks to blogger Luboš Motl for bringing that link to my attention.
You can see a complete list of past winners of the Nobel Prize for Medicine here.