I'll point out that though this instructable may seem long or complicated at first, it's only because I wanted to make sure it was well documented. It is actually VERY easy and VERY quick to do. Making these throwies should be just as easy, and take no longer than the original design. Once you've done one and you understand how it works, you'll be whipping these out in no time.
From the original throwie:
Developed by the Graffiti Research Lab a division of the Eyebeam R&D OpenLab, LED Throwies are an inexpensive way to add color to any ferromagnetic surface in your neighborhood. A Throwie consists of a lithium battery, a 10mm diffused LED and a rare-earth magnet taped together. Throw it up high and in quantity to impress your friends and city officials.