According to a Lifehacker write-in tip, you can make an ice pack using Dawn dishwashing detergent (and a zip lock bag). I just did a quick test with a small amount of whatever detergent we have upstairs (it's not in the original bottle) and it congeals to a cloudy gel when frozen. Perfect! Being a big fan of post-workout icing (regardless of injury), I'm going to buy me like a gallon of Dawn and dump it into one of those huge freezer zip lock bags.
