Make your own Microphone in times of emergency.
I was watching this television show about gadgets and stuff and in the end they showed a crude way to build your own microphone in no time, in case of urgency. But this is not a replacement to your conventional microphone and is only meant to be used in case of an EMERGENCY.
This is how it goes:
Take your normal earphones that came with your i-Pod's or walkmans with the stereo jack or pin (whatever you wish to call it) on the other side. Attach it to your computer in the microphone's slot. And then open up Sound Recorder in Windows from Start->Programs->Accesseries->Entertainment->Sound Recorder or if you don't have it installed at this location you can search for the executable at %Windows_Installation_Directory%\system32\sndrec32.exe. e.g. on my machine it was located at c:\WINNT\system32\sndrec32.exe. Just press the record button and start speaking on each of the earphone one by one. You should see sound waves in the Sound Recorder. By speaking in the earphone one at a time you can figure out which one works best and then use it for your purpose. But this is not going to replace your microphone as the sound quality is not as good as it should be...

Now, the question that must be popping in everyone's mind (like mine) must be that how can something like that work? The answer they gave on the show was: the way these earphones and microphones are manufactured is almost same. I am NOT convinced by their answer, so am still searching for a satisfying answer. Will post it when I get one...