Q. Where can I find information on homelessness in major cities?

The National Coalition for the Homeless is a good place to find statistics about: homeless numbers, why people are homeless, HIV/AIDs and homelessness, homelessness and children/veterans/youth/LGBT, unemployment/employment issues, and much more.

Additional information can be found at:
U.S. Department of Health and Human Services - Homelessness
U.S. Department of Housing and Urban Development (HUD) - Homelessness