I am a HUGE advocate of USB headsets.
Reasons being:
1.) Simply plug in and it works (You may have to choose the headset depending on what you plan to use it with, but other than that it just doesn't get any simpler.)
2.) With a USB headset, the soundcard is built into the headset. This means you can have your game sound go through your speakers and have teamspeak, ventrillo, or other programs use your headset.
3.) Voice recognition has always been better with USB (in my opinion)
4.) In line mute button is digital so usually works way better than the analog version. This also makes the need to use "push to talk" a thing of the past. (Setup voice recognition then just use the in line mute button when you wish to chat or not.)
My personal favorite headets are from
www.plantronics.com although i'm sure there are better.
-Edit-
This site is pretty darn good for finding deals...
www.pricegrabber.com
Just type in "plantronics dsp"
I purchased (2) DSP 300's for a combined price of $51 (Including shipping)