How do I pack a road wheel for shipping? I need to ship a rear wheel back to the manufacturer for a warranty issue (Mavic).  I'm wondering what the best, most secure way to package it is so that there can be no refutation that 'it was damaged in shipping' or something like that.  

What materials do I need and how do I package it?  I want to do it on the cheap because the manufacturer isn't covering the shipping cost.
Wheels generally come in a cardboard box with plastic caps over the hub ends to protect them and a bit of other padding (for skewers and the like) added in.  Your LBS may have a few of these laying around for whatever size wheel you are sending back.  They may even be willing to do the package job for you and save you a bit of time for a reasonable amount of money.  If you just want the materials, I have known some shops to simply give them away (especially to known customers).

The stresses a wheel endures in a cardboard box during shipping are less than what they would endure properly installed on a bike.  Any damage more than that would completely destroy the cardboard box and be evident as a shipping mishap.  I recommend insurance from your shipper to protect against such mishaps.