Who needs a car to haul moderately heavy stuff? Not the bicyclist with a Surly Trailer tethered to the rear of their bike, who can use it to pull 300-pounds of gear in relative convenience.
Granted, you'll have to expend more leg power than usual to pull anything that heavy. If you've got the muscles for it, though, it's pretty nice to have the option to leave the car in the garage and push pedals when you have a load to bring in tow.
The Surly Trailer hooks onto both sides of the axle in the back wheel of your bicycle, provided your wheels fall within the 20- to 29-inch range (it has adjustable height). It's available in two sizes, short (32 inches) and long (64 inches), each of which can carry Brock Lesnar like it's nobody's business. Both models come with two 16-inch wheels.
Most bikes should be compatible with the trailer, save for Surley's own Pugsley and Big Dummy axles. For those who like to tinker with their accessories, it comes with DIY mounts, so you can install whatever you want atop the frame, like stripper poles (for your mobile burlesque show) or a bed (in case you're living in your bike).
But why not just get a cargo bike? Because few cargo bikes can carry that much weight without losing balance. Plus, with a trailer, you can use your bike sans a cargo bay any time you want to. The only likely caveat for the Surly Trailer is the price: $750 for the short and $770 for the long. Expensive. It won't be out till Spring 2011, though.