To me, loss of freshwater supplies is the scariest impact of climate change. After all, I can imagine adapting relatively successfully to a warmer world. I cannot imagine adapting to a world with less freshwater. That view was reinforced by a great article on water in The New York Times Magazine. Read it and then forward it to all of your friends.
Over on inkstain, John Fleck also has a bunch of terrific blog entries about the ongoing water crisis in the Southeast U.S. In his latest entry, John points out that the drought there, while bad, is not that bad from a historical perspective.