Dang, that grossness just sneaks up on you. Pulled all the shelves, gave em a good wash.
Conclusions: Dairy leaks. Even in sealed containers. Not much can be done about this aside from wiping the shelf down regularly.
Produce: GAH. Try not to buy it until I need it. If I don't need it, I shouldn't buy it. I recently read an article that says mixing produce, even if it is only two days old, is a bad idea because it causes enzymes to be shared.
Aside from keeping everything in containers, I'm not sure what else can be done.