For several years, the only places to find online U.S. Census records was Ancestry.com (rather expensive), Genealogy.com (also expensive), or at HeritageQuest Online (free to users but only available through subscribing libraries). These were the only sites to carry the images of the original records for entire states. It seems interesting that in the past few months, other web sites have started offering access to the same census record images and indexes.
The new pilot project of FamilySearch, owned by the Church of Jesus Christ of Latter-day Saints, has the 1850, 1870, and 1900 U.S. Census records available free of charge. Some of the records are not yet complete. For instance, only 15 states' records are available today on the site. Details may be found at http://pilot.familysearch.org/recordsearch. Massachusetts and Wisconsin state census records are also available at the same location.
Footnote.com now has the 1860 U.S. Census records online as part of its Civil War Collection. This copy of the U.S. census is completely indexed. While not free, the access is cheap at $7.95 a month for unlimited access. Details may be found at http://www.footnote.com?xid=46.
The images on Footnote and the pilot project of FamilySearch are sometimes better than the other services. The search methods are also different. For instance, the viewer software on both Footnote.com and FamilySearch is better than on the other services. You can easily adjust brightness and contrast, or invert images.
Footnote.com's new Advanced Search also lets you search by First Name, Last Name, Place, Age, Birth Place, Color, County, Family Number, Minor Civil Division, Sex, State, or any combination of those fields. If you are having difficulty finding a female ancestor whose maiden name is unknown but you know she was fifteen years old at the time of the census, you could search for all the 15-year-old females in the county with her first name.
The new sites have also created new indexes. If a person was "missing" in your previous searches on the old sites, you might try again on FamilySearch and Footnote.com. Their newly-created indexes may have located someone who was not listed in the older indexes.
It is great to have choices. We now have more choices than ever before.