Employer's Corner
What can't be asked at the interview by US companies (according to the EEOC):

Your age
Date of birth
Birthplace
Ethnic background
Religious background
Religious beliefs
Native language
Maiden name
Marital status
Date of marriage
Whether your spouse is employed
How much your spouse earns
Whether you are pregnant
Whether you have had an abortion
The number of dependent children living with you
To explain all gaps in your employment record (i.e.. to determine if 
you have taken time off to have children).
Whether you have any physical or emotional defects. However, an 
interviewer can ask whether you have any job-related defects.

Note: It is now necessary to prove U.S. citizenship. If you do not have 
a Social Security Card, you will have to produce your birth certificate 
or a certified copy. The birth certificate, of course, reveals your 
date of birth and age.