The Cart Bike doesn't turn corners very well, admits the second-prize winner of our TreeHugger/Popular Science/Instructables Go Green contest; plus, we're not entirely clear how stable the setup would be with a week's worth of groceries, but it's still a nifty concept if you happen to find a derelict shopping cart gone astray. (We probably don't need to remind you that stealing's a big no-no.)
Besides the bicycle and shopping cart (thank you, Captain Obvious), you'll need socket and hex-key sets, a dremel tool, a utility knife, some zip ties, a rotary tool, and a screwdriver. Once you've acquired your hardware, all that remains to be done is to bolt the cart to your bike with a little handlebar surgery.
Think you can design a better Cart Bike? Let us know in the comments. ::Instructables
Difficulty level: Moderate