A good microphone for use only to use 'Speech' commands in Mac OSX

[MythicFrost]

I'm looking for a good microphone to use the speech settings in Mac OSX, I'm not sure if the Mac Pro comes with one built in or not, but either way, it can't hear me =)

So I'm wondering if anyone knows of a good quality one, perhaps one that simply clips on to the screen, or plugs into a USB slot on the screen, so I can talk to my Mac?

Kind Regards
Me