I found this USB soundcard on DealExtreme for less than $3 and shipping is included as always. I originally bought it for my PS3 because I wanted to use my PC headset/mic. It works fine with the Playstation 3.
Then I figure I’d test it out on my homemade Mac just for kicks. To my amazement, it works without any modifications. I have Snow Leopard 10.6.1 and when I plugged it into an available USB port, it was detected by the OS. I didn’t have to do anything.
As you can see, it shows up as “USB AUDIO” on my Mac.
So all you have to do to have sound come out of this device as opposed to your internal sound card is choose “USB Audio”. If you plug up a microphone, you can choose it as an input too.
So for less than $3, this is a great deal! It works on PC/Mac/PS3 and possibly other platforms I haven’t tested on yet.
DealExtreme: USB Soundcard