Occupational Outlook Handbook, published by US Department of Labor every two years, is a great resource of career information. Check out this fresh-from-oven 2004-2005 Edition. For every one of the hundreds of job lines it covered, there will be a description of the nature of the job and work conditions, current employment status, training and qualification requirements, job outlook and earning power.
Also, be sure to read the section Tomorrow's Jobs for some big trends, like:
1. "The U.S. population is expected to increase by 24 million over the 2002-12 period," and "[c]ontinued growth will mean more consumers of goods and services, spurring demand for workers in a wide range of occupations and industries."
2. "The civilian labor force is projected to increase by 17.4 million, or 12 percent, to 162.3 million over the 2002-12 period."
3. "Total employment is expected to increase from 144 million in 2002 to 165 million in 2012, or by 14.8 percent." (MM: Total employment number is higher than civilian labor force as some workers may have more than one jobs.)