I forget what I was searching for, but I found this old video of the US Government disposing of old metallic Sodium after WWII.  Sodium explodes/burns when it comes in contact with water.  According to the narration on the film, the government couldn’t sell the sodium because no one would ship it to a buyer because it could explode so easily.  (Water really is everywhere).  So the government just found an old, dead lake, and tossed the barrels in, and watched em  explode.  I’m not sure what the environmental impact of this really is, but it’s cool to watch anyway.

http://video.google.com/videoplay?docid=
3825610222960975525&q=sodium+lake&hl=en