I just successfully hooked up an electret microphone to my PC, without burning either. I use a very simple circuit to pre-amplify the signal, using a single general purpose transistor (2n3904). The microphone is electrically separated from the amp by a capacitor (.1 uF). The same trick (.01 uF) is used between amp and PC.
Audacity is able to record sound and display levels. I am getting decent range across the audible spectrum.