I read a lot of Lifehacker and other organizational blogs. The trend these days is GTD. Basically, you keep and manage lists and ideas on a series of cards, in folders, whatever. This is my implementation of that. (this has also been called a Hipster PDA as well.)
What I use are Mead Ringdex cards..
Now, the ones sold at walgreens are good but the rings are too big. I replaced them with a 1 inch ring so the card stack can be smaller and the rings can be about as big as the stack.
This has the nice side effect of making the stack 'lockable'. So you select the page you want and flip it open so it's on top. You then fold the rings over the top and bottom of the stack and your page is always open.
The nice thing about having these colored edges is that they give a border to your cards where you can easily write a label. I did that for a while, then discovered that I didn't need the full length for labeling, and if I cut some of the edge off I've got tabs!
The last modification I made was to add an envelope. I was envious of people with moleskine notebooks that had a nifty foldy pocket for holding random things, so I created my own out of 2 plastic ringdex covers and some tape.