Having been stuck in the analog world for awhile, partly by choice, partly due to the implosion of my trusty Palm IIIx, I would like to offer some thoughts on pen/paper solutions:
I have reverted to my favorite analog notetaking tool, the http://www.blacknred.com A4 hardcover notebook. This is in the European A4 format, and is sold in the US at such places as Office Depot. It's a great book - great value and solidly made. Somehow it just works for me. Despite attempts at other systems, I find I am better off with a consecutive record of notes, and then to transfer the important info to a more highly categorized system. The hardback / bound nature of the notebook makes it very easy to write when on the run.
I have not found the A5 version of this in the US - a previous poster mentioned this - does anyone know where to find it - I found the spiral version only.
Another favorite of mine: The Rite in the Rain all-weather notebook http://www.riteintherain.com. I use the smallest version, and slice it in two - the half-notebook fits in my back pocket and takes amazing punishment without falling apart.
Finally - the Moleskine 'classic' notebook is just phenomenal. It is effectively a mini version of the Black 'n Red - great form factor, famous history, etc. It also has a great pocket in the back for collecting receipts and business cards. Highly recommended, available in the US and internationally, made in Italy I think.