USGenWeb Free Census Project Help, Where to get Census Records for Transcription - National Archives
The Federal Government maintains Regional Archives which have the federal census microfilms. If you have one of the Regional Archives available you can use the census films there. This site lists the locations by state/area.
The National Archives page "What Census information can I get on this web site?" has much useful information for locating records.
National Archives also sells microfilm rolls. Check the website for current ordering information and costs.