I need to work with census data and don't know where to start.

There are a number of resources you can use to learn about and use census data. The ISSR Data Archive maintains a collection of census data covering many years and countries.

http://www.sscnet.ucla.edu/issr/da/catalog.htm
http://www.sscnet.ucla.edu/issr/da/index/techinfo/M7891.HTM

The Census Bureau provides options for making tables and downloading reports, maps and tables.

http://www.census.gov/main/www/cen2000.html

Other useful census data sites:

http://www.ats.ucla.edu/stat/census/
http://www.icpsr.umich.edu/CENSUS2000/