Also used to describe recruiters, often derisively. Head-hunters are hired by companies to fill vacancies in their staffing positions. A good head-hunter can negotiate a very lucrative deal for you to the benefit of everyone involved (you and the head-hunter because you get paid well, the company you work at becase they get an excellent worker.) A bad head-hunter does nothing but take money from you both without adding any value.

In my experience as a contractor, a head-hunter will get anywhere from 30-50% of my hourly wage (i.e. I'm paid $50/hour, they'll bill the company I work at at $75/hour.)

Until you've got a couple of jobs under your belt, head-hunters will be a Necessary Evil. Even then, large companies (the HPs, Ciscos and Suns of the world) will only hire you through an agency because they've got more money than time.