There is also a public thread for further discussion and recommendations.

Plantronics and Sennheiser both have universally good microphones. They pick up your voice well, don't have a tendency to get in your breathing path, and do a very good job of ignoring background noise. Pick whichever model you prefer for comfort or budget.

Just make sure you get a USB one, or all that goes to waste when your onboard sound introduces noise, buzz, crosstalk, feedback, echoes, etc.

The Plantronics are more available retail, Best Buy and Fry's in particular. The Senns can be had for far below MSRP on Amazon/etc.

Logitechs are popular, and can usually be made to work, but prone to problems and even at their best never sound as good as the others. Their mics pick up background noise (computer fans, keystrokes, etc). Their USB adapters are not noise-free like most, they seem particularly susceptible to any noise introduced by your power-supply and/or devices (so while one person might give you a good review of a logitech, you may very well have a different experience). Given that the Plantronics are just as available retail, and neither they nor the Sennheisers are any more expensive, don't put yourself or us through the hassle.

Those are the three major brands we come across. Strangely, this seems to be one market where brand matters more than model. Logitech makes 'peripherals', Plantronics makes (mostly phone call center) headsets, Sennheiser makes (generally high end) audio gear. Click on those three home pages and tell me who has a vested interest in keeping their audio credentials intact ;)