Yes, you can buy a BT USB dongle to plug into your PC or notebook that will connect with a BT headset and use it for VoIP and online gaming.

I bought the Plantronics 640 BT headset http://reviews.cnet.com/Plantronics_Discovery_640_Bluetooth_headset/4505-12523_7-31515626.html when I upgraded my cellphone and it works well with my cell and notebook when I use Skype. But instead of a USB dongle I'm using a BT PCMCIA card. It's less obtrusive than a dongle and doesn't use up a USB port. A minor problem you might encounter while using the BT headset is some interference if you're near a cordless telephone that's in use since they both use the 2.4 GHz frequency, although I haven't encountered any problems yet.

Cheers.