The topic of working with recruiters comes up frequently in my line of work. For every person who has actually used a headhunter, there must be at least three who are unsure how to start or believe that this is the solution to finding a job with minimal effort.
This ExecuNet article brings up excellent points for candidates seeking the services of a recruiter: http://tinyurl.com/gfpay
To reiterate, recruiters do have your best interest in mind and are trying to make that perfect match happen. Establish a good working relationship with one or two headhunters in order to benefit from this arrangement.