America's Salaries and Wages Survey
HD 4973 .A63 2007 - Young Library Ready Reference
Includes salary information for more than 2000 occupations in numerous locations around the United States.
Bureau of Labor Statistics - Wages by Area and Occupation
Information about wages for numerous occupations at the national, regional, state, and metropolitan area level.
Location and Cost of Living
Overviews, data and future projections on occupations is another type of background information.
It is likely that your chosen career path has at least one (if not multiple) professional organizations associated with it. You can use this free US Government site, CareerOneStop to search by industry, occupation, or association name for your chosen profession.
Additionally, a few example organizations are listed below.