Plantronics makes top-rated bluetooth headsets that are super light, sound great, and look really cool. I recently acquired the Plantronics Voyager PRO because it lets me connect with both my iPhone and my computer.
That means I can use it on the road for hands-free phone conversations in my car, and I can also use it for Skype calls on my computer (or with my VoIP softphone that lets me dial anywhere in the world over the internet, without paying long distance rates). You can get a Plantronics bluetooth headset here on Amazon for under $70.
Connecting the Plantronics Voyager to my iPhone was a complete breeze, but getting it to work with my computer took a little persistence and eventually an operating system upgrade to Mac OS X 10.6.8. It turns out there was an incompatibility with OS X version 10.6.6 and the Plantronics headset, that wouldn't let it be recognized as an audio device no matter what I tried.
Fortunately, upgrading to OS X 10.6.8 solved the problem, and here are the steps I took to connect my Plantronics Voyager PRO to my Macbook Pro and use it as the audio device for Skype, iTunes, or any other sound application: