I bought the DLO Action Jacket from everythingipod. Nice case I love it. It is made of neoprene, I have the dark blue version it comes with a swivel belt clip and an arm band for working out. Well worth the $29.99.
Another case that is shipping is the SportsSuite Convertible. It is neoprene as well and comes with a removable cover that carries yopur headphones as well.
There is another couple cases made by vaja that are shipping but they are super expensive as you go up the line. They are all leather though.
One new case to hit the scene and that will be shipping soon is from booqbags there's is very cool it is made from tough and weather-resistant 1680D nylon - virtually indestructible. The front cover snaps on using two tiny magnets. I am sure the iPod must be suffeciently magnetically sheilded.
Hope that helps,
Mike
P.S. I am still waiting on my stupid iSkin from iSkin.com, I recomend the think different store.