My 360 was crashing a lot (like once every 20 minutes). So I took the power supply off the ground and suspended it in the air with some string. I have been playing for about 3 hours straight and no crashes so far!
EDIT: I found an easier way to do this. I got a box with no cover and put the power supply on the edges.
Pics (hosting provided by www.photojerk.com):
EDIT 2: This is just one way of doing it. The main point of this fix is to get your PSU off the ground for maximum heat release.
Also, it seems like most 360s are freezing due to overheating. My Xbox 360 was freezing every 20 minutes. When I put the PSU on this box I left the console on for 7 hours without crashing (I finally decided to turn it off).
NOTE: If your 360 is not freezing because of overheating, the above fix WILL NOT work.
EDIT 3:Another member of Gamespot, howoldareyou, has discovered another solution to the 360 freezing that he claims solved the "three red lights of death problem" for him.
Here is his post:
"Helllo all, like many other unfortunate individuals who fell victim to the 3 redlights of terror I decided to do some deduction problem solving. My system flashed the 3 redlights while playing "Call of Duty" and refused to turn on for days afterwards. i did everything M.$ suggested (dissconnect everything and reconnect). It wasn't until I realized that maybe it's the source of power that is the problem (Follow me). If you are plugging your Xbox360 into a cheap surge protector or general plug strip you might want to plug your xbox into a very good quality protecctor or plug it in the wall. I plugged mine into the wall and VOILA it works flawlessy......plug it back into the power strip and it works for about 10 minutes...plug it back into the wall and VOILA it works perfect again. It's been running solid for 14 hours straight and no problems have occured in the past few days since it's been plugged into the wall
I think the power brick is overly sensitive to Good CLEAN power. A cheap protector or plug strip might not be providing the proper flow of power to the unit. Anyway, when I plug it into the strip, the xbox will start to do the 3 redlights (except the upper right one) which indicates a hardware failure. I'm troubled to think that the many people who returned their unit, only to get a new one that does the same thing, when the real problem is where they are plugging in their unit./ ANYWAY, it works for me...hope it works for you. provide feedback and let us know."
Here is a link howoldareyou's topic: http://www.gamespot.com/forums/show_msgs.php?topic_id=24054545