Over the years Katia used several different gears to sing in SL or Live around town. Here's her current set up:
This is pretty much all you need ( not necessarily in this quantity) One Mac, a Mixer, a Mic and a MP3 Player.
Audio Technica ATM 4050
I have and had many Mic's but along with the Seinheiser EW100 this one is my favorite of all times.