Free GM Resource: PocketMod
You could have an idea for a campaign, an adventure, maybe some interesting trap design....who knows?
I've tried carrying a small notebook around and I'd be good for a couple days before I either forgot it somewhere or just misplaced it at home. Obviously in a pinch any old piece of paper will do.
This week's Free GM Resource falls somewhere in between. PocketMod is this awesome website that does one simple thing well: help you create small disposable mini-notebooks. For the cost of a sheet of paper and some printing (essentially free), you can have your own custom notepad.
I prefer to use the storyboard layout along with a few pages of lists and graph paper. There is a good selection of pre-designed layouts you can string together. New since I used the site last is a downloadable PDF to PocketMod converter. I'm thinking that I might use that as a player to create some small custom spellbooks.
I highly recommend you checkout PocketMod.