You might find this suggestion a bit goofy, but I picked up a cheap $15 over-the-head type headset manufactured by Sanyo at Wal-Mart. It's so comfortable that I forget I'm wearing it. It's not what I would call "heavy duty," but it is very lightweight, and has a mute/answer/end call button on the cord that works great with my BlackBerry. Sound quality at both ends of the call is very good.

I also have a Bluetooth headset for traveling, but I find the the cheapo Sanyo headset excellent for when I'm working from my home office. Never needs charging, either