Bah!
Freezer temperature is colder than ice water...
To get your beer *really* cold, crush the ice straight from the freezer. Get a bag of rocksalt and add some salt to it to get it a little slushy. THEN spin your beer in it. Keep the slushy mix in the freezer between beers so it doesn't warm back up. Your beer will get colder than in icewater, and it'll get colder faster.
The rate of cooling is related to the difference in temperatures between the two areas in contact. (A fun application for differential equations/calculus. Spinning the liquids keeps thermal layers from forming. To understand what I mean, get a long straw and a pitcher of warm water. Fill the pitcher 3/4 full with warm water. Carefully put an icecube tray's worth of ice into it. Take a sip from the top with the straw after a few seconds... cold. Take a sip from the bottom with the straw... warm for a while. Convection currents will eventually mix the liquid to a more uniform temperature, but this takes time. Spinning the can provides a mechanical current to mix it quicker.
I haven't tried it before, but if you've got an extra storage freezer, I'll bet you can find the right mix of ice and salt that will remain slightly slushy in your freezer, even when not used. (provided your freezer isn't set below 0 degrees Farenheit). I'm not sure, but if it is, a mixture of salt and sugar may lower the temperature even further than 0... interesting experiment perhaps for kids.
And... I love pepsi when it's just barely turning into slush on the top... Something easy enough to achieve just by leaving it in my car lately.

(