Need a microphone ? Which one to buy ?

Hello All

I need a microphone ( p2 or usb ) to use with mac mini. Which one would you recomend and where can I get it on the web ?

What are you going to do with it? it will greatly affect what we suggest :)

Sorry for not inform that before. I am going to use the mic with voip applications on my car. I am not sure yet if I am going to put it on the front panel or attach it at the rear mirror - it will depends on the mic