I bought a Nokia BH-214 th other day, and have been really pleased with it.

Over my previous bluetooth headset, it has great sound, a good range. The charger socket fits my nokia charger so I only need one! (I use the 2mm to microusb adaptor with the N900), and I can use the earphones which suit me, which is important as a lot of them don't fit correctlt or comfortably.