For the uninitiated, a Hipster PDA is a collection of 3x5 cards. While using a binder clip to hold together a bundle for easy portability is very handy, I'm a proponent of using a "jotter wallet" to hold the cards. I've been using one similar to this for about three years now, and I'm never without it handy. Mark writes about a slightly different style that is available from Eastgate Systems. My friend Ron uses a Pocket Briefcase from Levenger.
I normally carry about 6 blank cards, a business card, and a few playing cards in case I have an opportunity to pitch a little Three Card Monte. The overall package, not counting the Fisher Bullet Space Pen that I carry in my front pocket, is a barely noticeable 1/4 inch thick. At the end of the day, any notes that deserve permanence are transcribed into Tinderbox. (Some might call this synching.)
Those of you still lugging around battery-powered, chip-driven PDAs should try a Hipster. It's retro-cool.