I play in Second Life several hours a day. I had a 10 years old microphone. So, recently am shopping for a headset.
There are lots of headsets out there, from $10 to over a hundred. If you use headset casually, such as 30 min a day for online voice chat, then any $20 ones will do fine. I would recommend Microsoft, Logitech, or Sennheiser brands.
If you use headset for more than 1 hour a day, then, you need something comfortable, high quality, and with good microphone.
For gaming, you want the headphone part to be high quality too, because otherwise music would sound bad, or you don't get the thundering “boom” effect when bombs go off.
Microphone is also important, because it'd be a headache when you trying to voice with someone and the message is repeated “can you hear me? can you hear me alright?”.
There are 2 connector types for the headset. The cheap ones use analog plug, the same ones used in music players. One plug for the microphone hole and another for the headphone hole. Better ones, usually over $20, uses USB. USB is better because it is digital, and it's just a single plug.
After few hours of research, i end up buying “Microsoft LifeChat LX-3000 Headset”.
I do not recommend this. Because:
If you want to spend more, i highly recommend: “Sennheiser PC151 Over The Head Headset” (with Noise Canceling Mic and In-line Volume Control) (≈$50)
Sennheiser is the best brand for high quality headphones. They are extremely light weight in comparison to similarly sized headset, and extremely comfortable for 5 or more hours of continuous wear.
I own a Sennheiser HD 570 headphone i bought for $120 in 2000. Now, it's been 10 years, and i still use it! The sound quality beats any headphone or hi-fi speakers that cost thousands of dollars.
This one is highly recommended.
For webcam i recommend: “Microsoft LifeCam Cinema”.