These links will take you to external websites
USGenWeb Census Volunteer link
USGenWeb pre-1950 census project
LDS Volunteer Projects
Check Cyndi's List for a comprehensive look at the Colorado census
about.com has a list of volunteering links
Volunteer Projects Help Family Historians by Sherri Bradley Apr 23, 2010
For those looking forward to the 1950 census release in 2022
Note: Ancestry.com (not free) has ALL censuses from 1790-1940 digitized with super clear images. The only problem, ancestry at one time tried indexing using non-English speakers with disastrous results. In one instance, my surname, Cooley, was indexed as "Coalson".