Example of the sound quality you can get out of this:
Step 1: What You'll Need
2 Male RCA to Female 3.5mm Adapters:
2 3.5mm Microphones:
As user Rogue Agent pointed out in the comments, you should take a look at the frequency range of the microphones you're buying. The ones I linked to are made for voice recording, so they aren't the best for recording music/sound. Human hearing range is about 20Hz - 20kHz, so microphones closer to that range would work better.
Step 2: Put It Together
Protip: Use the picture as a guide.
Step 3: You're Done. Now Put It to Use
Anyway, enjoy your new stereo microphone. Use it in place of your camera's horrible sounding built in one, or to record ambient sounds. Did I say that already? Oh, whatever.