All, the memories this invoked.
Remember those days of youth, those of us in our forties? Remember algebra and calculus prior to the pocket calculator? Remember slide rules?
Scientific American has a great article by Cliff Stoll (he of "Silicon Snake Oil" and "The Cuckoo's Egg" fame) about them, and you can download a PDF version of the cut-n-fold paper version here.
Trust, nothing but nothing says geek like a slide rule. Now, you too can recreate those wonderful days of yore, and even reenact that great scene from "Apollo 13" where mission control had to calculate another delta V for the crippled spacecraft (though slide rules really wouldn't have been used for that...). Stick it in your white shirt pocket replete with protector.
Okay, it'll look a little too geeky. Still, for those of us who had to suffer these things, thought this would be nice.