Feed from headphone/speaker out jack on the scanner into the microphone/line-in port on computer using standard 3.5mm stereo plug cable. Using a regular microphone is not recommended as it would pick up background noise. The cable is the best method.
There are cheaper solutions for USB input also. Although this is not quite what I was looking for there are ones that look just like this that have a Line-In instead of a Mic-In: