On January 15, 2009, many federal contractors will be required to use the E-Verify online system for employment eligibility verification in addition to I-9 procedures. Here are links to information about E-Verify.
E-Verify FAQs for Federal Contractors
http://www.uscis.gov/files/article/FAR_FAQ_13nov08.pdf
E-Verify Memorandum of Understanding for Federal Contractors
http://www.uscis.gov/files/nativedocuments/MOU.pdf