This website provides detailed job descriptions and data. You can search or browse by industry, title, or category (like level of education/experience needed, career clusters, or expected growth).
Scroll down the page to access the 2010 SOC System, used by federal agencies to classify workers into occupational categories, which helps them track, collect and report data. (Replaces the Dictionary of Occupational Titles.)
Note: Only participants and subscribers can access the full data, although much of the data is used in press release information. You can access the top level data for free.
This website contains the Bureau of Labor Statistics' Employment Cost Index and Employee Compensation. Free access - scroll down to click on the databases or tables.