>Gears and Wears>How do you keep your iPod dry?
Your toughness is made up of equal parts persistence and experience. You don't so much outrun your opponents as outlast and outsmart them, and the toughest opponent of all is the one inside your head." - Joe Henderson
I use this http://www.amazon.com/gp/product/B0013BC7XS Under wet and sweaty conditions, they recommending applying a piece of tape to the exposed end.
I just picked up a couple of these Amphibx waterproof armbands for my wife and me. (iPhone 3G and 3Gs) I've only done one run with it so far, but besides being a little bulky it seemed to work great.
Loves the outdoors
I just use a ziplock bag. If it's really heavy rain, I use two.