If you're hoping to earn more money at your job (Who isn't?), then you cannot afford to miss the New York Times piece on using the internet to gain leverage in your salary negotiation. This is the most important paragraph from the article:

New Internet technologies are providing information that has never been available to the average person and transforming the way they sell homes or buy airline tickets. It could have the same effect on the 47 million people who look for new jobs each month and the countless others who think they are underpaid at the ones they have.

What sites like Salary.com and PayScale.com are doing is establishing a more efficient marketplace. Just a few years ago, you would have had to spend hours on the phone to find the best deal for a plane ticket. Now, you can log-on to a site like Travelocity, and browse rates from all the major airlines. Likewise, access to more information about salaries will provide employees with the information they need to know if they're being paid an amount comparable to what they might earn elsewhere.

Most interesting, PayScale.com offers information on jobs where it's typically hard to find data, including porn star, crossing-guard, or Rabbi.