If you buy a case of beer -- especially lousy American macrobrew -- that's sold at room temperature, it will need to get cold before it can be enjoyed. Putting it in the fridge is okay if you plan to drink it in a few hours, but generally the need for beer implies the need for beer fast. The freezer is another option, one which will get the brews decently cold within perhaps thirty minutes. Unfortunately, finding the freezer space for even six beers, let alone an entire case, may be difficult, and if forgotten in the freezer for too long the cans will explode.
There is a better solution to the problem, and one that can be easily extended to as much beer as one needs to chill, even an entire keg. It is simply an extension of the traditional way of freezing homemade ice cream, the use of salt to decrease the freezing temperature of water. That is, just get a cooler full of ice as per usual, then dump a bag of rock salt into it along with enough water to get everything wet. Stir the beers in, close the lid, and wait for fifteen minutes or so. Voilà, you have nice cold brews.
This works because the salt lowers the melting point of the ice. If you throw the beers in a bucket of plain ice, they will be exposed only to the melting temperature of the ice (0°C) by the already-melted water on its surface. If, however, you're working with a 1:4 ratio of salt to ice, you've made it much easier for the ice to melt -- about 17° easier, in fact. That temperature approximates the temperature of a regular freezer, and since the beer cans are in constant contact with liquid of that temperature they can shed their excess heat pretty damn quickly. If you're worried about ice crystals forming in your keg or some such, just decrease the amount of salt added and the final melting temperature will go up.
Thanks to Playboy magazine for the inspiration, and our friend the Internet for the facts.
Spuunbenda says Wouldn't it speed up the chilling if you jar the cooler occasionally to stir the beer inside the bottles? Might shave a couple of minutes...