Reddit mentions of Rite in The Rain #7511-M Waterproof Ink-Jet Paper

Thanks for posting that, I never even thought to check for weatherproof copy paper. I print quite a few maps so that could be really handy.

If you have access to a laser printer, this stuff looks to be considerably cheaper per page and you can buy a smaller quantity to test it out:

http://www.amazon.com/Rite-Rain-Weather-Copier-25-Pack/dp/B000KEJX90/

Rite in the Rain maintains an active reddit account and gives useful advice on /r/pens and other subreddits. They of course push their products, too, but only when appropriate. I've got a few notepads and it seems like good stuff.

EDIT: Just noticed the inkjet paper, a bit more expensive though: http://www.amazon.com/Rite-7511-M-Waterproof-Ink-Jet-Paper/dp/B002XQT8WU/