Thomas Keller at the LA Times has the details:
Rather than cooking the food using an immersion circulator, you can achieve similar results using a large picnic cooler and a probe thermometer.It's worth clicking through since they also have a video from Rory Herrmann showing how to wrap and prepare some fish and chicken in a water bath on the stove (though I might call it poached, there is no need to quibble) and some additional tips and recipes.
Here's how you do it: Fill the cooler with hot tap water to preheat for 10 minutes and then drain. On the stove, bring water to the desired cooking temperature (you'll probably need to fill a couple of stockpots). Then transfer enough hot water to the cooler to fill it nearly to the top, reserving some water for later temperature adjustments.
Add the food and then check the temperature of the water and adjust as needed. If the temperature is too high, pour in a little cold water. If it's too low, add in some of the reserved hot. A good-sized, well-insulated picnic cooler with its lid on (we use a 28-quart picnic cooler) should maintain an even temperature for around one hour. For slightly longer cooking times, check the temperature periodically and adjust with fresh hot water as needed.
For even longer cooking times, you can use a pot of water on the stove, though it will be more challenging to control the temperature. If you do elect to cook on the stove top, keep in mind that a larger body of water will maintain a steadier temperature, so select a pot that is large enough for the meat you're cooking and an ample amount of liquid. Depending on how much control you have over the burners on your range, you may want to purchase a tool called a diffuser from your local kitchen store to provide separation between the pot and burner, making it easier to keep your water at a sufficiently low temperature.
While I've always been more of a project oriented cook who enjoys a nice long afternoon working in the kitchen, it's hard not to see the benefit of sous vide for a perfectly cooked burger or chicken breast... and I've been meaning to try the beer cooler method since I saw it on Serious Eats over a year ago. Seems like a good thing to try out before going all in on something like a Sous Vide Supreme or even a PID controller and a rice cooker.