FirstGear has a new line of waterproof duffel bags. If you're on the Atomic Moto mailing list then you've probably already seen this...
I've been using Cabela's dry bags but looking to upgrade to something more durable. The FirstGear bags have a decent price.
those look nice, I currently use this: http://giantloopmoto.com/products/great-basin-saddlebag/
as well as a few of these: http://www.kriega.us/bike-packs/ a little expensive but works well.
I have the Giant Loop Coyote, nice for smaller bikes. I use a dry bag for the tent, and extra storage. I see Giant Loop makes dry bags too, they're kind of small though.