You can also pump ice water (via a submersion pump) through the immersion chiller you probably already have. That's what I do.
I put the immersion pump (bought a small one from Lowes) in a bucket of ice water and it pumps through my immersion chiller. I have the first minute or two of water go down the drain, because it's hot and will needlessly melt your ice, so you may have to add some more water or ice to your bucket during this time, but once it starts returning water that isn't super hot, you just divert the outflow from the immersion chiller back into the bucket.
I timed my last chilling and I took 7 gallons of wort in my kettle from boiling to 70F in 13 minutes, to 56F in 22 minutes (total), and was at 50F (lager pitching temp) in 27 minutes from start.
This does require some swirling of the immersion chiller to keep the wort from insulating itself as it does when it sits static.