There have been reports of the potential for scams related to the 2010 Census. Listed below is information from (and a link to) the U.S. Census web page on this topic.
This looks like the best resource, it comes directly from the Census: http://www.census.gov/survey_participants/related_information/phishing_email_scams_bogus_census_web_sites.html
Also, this includes information about how to report such scams.
Phishing, Email Scams & Bogus Census Web Sites
What Is Phishing?
'Phishing' is the criminally fraudulent process of attempting to acquire sensitive information such as usernames, passwords, social security numbers, bank account or credit card details by masquerading as a trustworthy entity in an electronic communication. Phishing is typically carried out by email and it often directs users to enter sensitive information at a fake web site whose look and feel are almost identical to the legitimate one.
The Census Bureau does NOT conduct the 2010 Census via email or the Internet.
Census Bureau initiated communication through email
You may receive an email from the Census Bureau regarding your participation in a survey, however:
The Census Bureau does not request detailed personal information through email.
The Census Bureau does not send email requesting PIN codes, passwords social security numbers or similar access information for credit cards, banks or other financial accounts.
How to report phishing, email scams and bogus Census web sites
If you receive an email or find a web site that you suspect is falsely representing the Census Bureau:
Do not reply or click on any links within the email.
Do not open any attachments. Attachments may contain code that could infect your computer.
Forward the email or web site URL to the Census Bureau at firstname.lastname@example.org.
After you forward the email to us, delete the message.
You will not receive a confirmation email after forwarding the information to us. However, the Census Bureau will investigate the information and notify you of its findings. The Census Bureau can use the information, URLs and links you forward to trace the hosting web site and alert authorities to help shut down the fraudulent site.
Is your survey legitimate?
If you have questions regarding the legitimacy of a survey questionnaire received in the mail, a phone call or visit by a Census Bureau employee, or other concerns of a non-cyber nature, please visit our Are You In a Survey? page.