"Idealist is an interactive site where people and organizations can exchange resources and ideas," identify job and volunteer opportunies, etc.

Climbtheladder provides in-depth descriptions of thousands of job titles that provide information about requirements, job outlook, and advancement opportunities.

The Bureau of Labor Statistics under the US Department of Labor provides a handbook on occupations and their outlook for the future. It will tell you the training/education needed, earnings, expected job prospects, what workers do on the job, and work conditions.