"How much should I be making?" is the question I'm asked by many candidates. The answer isn't always so simple - it depends on the company. There are places like Salary.com or Payscale.com where one can do a salary comparison or see the average compensation package for someone in a similar position. Unfortunately, I find that the pay ranges are either off or too wide to be helpful on those sites.
Glassdoor was launched in July 2008 and the idea was to provide real salary packages and company reviews by employees. In order to see the full reviews and salary info, you must participate so be prepared to register and give your information (anonymously, of course).
I looked through some of the content on Glassdoor and I found many of the large PR agencies, but the mid-size and smaller agencies lack information. Generating user content is surely one of the greatest challenges for Glassdoor, but certainly over time it could become a heavily relied on source for employees and job seekers looking for information on company culture and fair compensation packages.