Raccoons are the major pest around here, though there were bear warnings in some of the campsites I stayed at earlier this summer. I forgot cord, so I tried sealing everything up in a plastic bag in a stuff sack inside my pannier, but the raccoons got to it:

New easy access port

Luckily, they just ate my bag of trail mix. I duct taped the hole in the bag, bought cord at a hardware store, and hung it the rest of the trip. I had no more problems, but my wife's advice is to seal food in barrier bags, then inside leakproof, airtight containers--essentially super ziplocs inside better tupperware. That way, if there's no locker or place to hang my bag, it should be ok.

I haven't tried them yet, but I'm going on another short tour next week and I'll see how it works.