Amazon.com: MAX9814 Electret Microphone Amplifier Board Module MIC Auto Gain Max 40dB/50dB/60dB Frequency 2.7V-5.5V with Pins for Arduino : Electronics
Mini Non-Amplified Electret EM56 Microphone – Rugged Radios
Electret Microphone - 20Hz-20KHz Omnidirectional : ID 1064 : $1.50 : Adafruit Industries, Unique & fun DIY electronics and kits