Yay! I'm not the only one that didn't know.
http://www.youtube.com/watch?v=avWs4-wD15w <- Cheapyd from Cheapassgamer.com showing you how to do the towel trick.
It isn't actually dangerous to do because the Xbox shuts off if it gets too hot. What you are doing when you wrap it in towels and turn it on is keeping all of the heat inside and causing the solder that cracked (Causing your red ring because the heat won't properly dissipate then) to melt back together. So if you actually leave it on for like an hour, you won't have to fix it again. I haven't had to anyways.
And sending your Xbox to Microsoft takes a few weeks, isn't free, isn't an option for someone who opened their Xbox, and just isn't as satisfying as doing a freakin' magic trick to make the red ring disappear.