When it comes to environmentally-friendly iPhone cases, brown is the new green.
Case-Mate's iPhone 3G / 3GS Recession Case is simplicity itself: a no-frills cardboard cover that'll set you back a measly US$0.99 for one, or US$7.99 for the "Bailout Bundle" ten-pack. If plain brown is TOO plain for your tastes, feel free to color/illustrate/Bedazzle it to your heart's content, then throw it away…er, put it in the paper recycle bin…when it's worn out or you're tired of it.
While Case-Mate's serious about saving the planet and your budget, they're not too solemn about the Recession Case, as some of the FAQ's make quite clear (example: "Q) Is this case flammable?
A) If you light it on fire it is"). They even provide an animated GIF to show you how to put the thing together:
(We're guessing that, thanks to said recession, they can't afford a FlipPhone to upload a video to YouTube…)