Wow -- Hawk's system is amazing!!! I spent quite a bit of time poring over his flickr set and then reading his blog. I prefer lined cards, but picked up some grids today I was so impressed with his logging system.

I think something similar to what he has done might be the easiest, most reliable way to organize, and that's to have each card/document marked at the top so you can tell at a glance what it is, then (I suppose) have a separate system for knowing where stuff is stored. Hmm, maybe a card catalog for your notes?

I don't know if this helps at all, but one moleskine system I saw was to set your moleskine up like a "blog." Number the pages, then at the front of each one, start a list for "categories" or "tags." Add to it as needed. Then whenever you write something new in the Moleskine, turn to the front and put that page number by the appropriate tag/s. I'm not sure if there's a variation on that for cards, but it's a way to be able to just write straight through a moleskine w/o worrying about keeping your info together in blocks that match -- just have the index in front.