There's a couple of choices here.

I use a basic headset that I got for free. It's basically this: http://www.amazon.com/gp/product/B0001NYK1G/103-6001458-7675818?v=glance&n=541966&n=507846&s=pc&v=glance

I don't use the headphones on it tho, I just put it around my neck upside down so the mic still reaches my mouth. That works fine.

Another option is to get a USB Headset. This will make it work like Xbox live: you can set it up so that all voice chat goes ONLY to the headset, and the rest of the sound comes from your soundcard. This is a pretty cool option, but I haven't tried it personally.

Maybe something like this: http://www.amazon.com/gp/product/B00005A9AU/ref=sr_1_2/103-6001458-7675818?%5Fencoding=UTF8