I have lived in Salt Lake County for over 2 years now, and am just now starting to take advantage of the free access to the HeritageQuest Online database. Through the use of my Salt Lake County library card number, I can search HeritageQuest Online from my home computer...for free.
You don't have to live in Salt Lake County though to get free access. I believe that most libraries around the country offer access to this resource. According to their site, "HeritageQuest Online is designed specifically for patrons in public libraries who are either just beginning their family research or who after years of work are still uncovering their past."
Records on this site include:
* The complete U.S. Federal Census 1790-1930 (they advertise a complete Census Record, but they don't actually have 1830, 1840, 1850, or 1880...and have only part of 1930 - you can find the 1880 Census for free though on familysearch.org)
* ProQuest's Genealogy & Local History Collection of 25,000+ family and local history books - every word searchable
* The Periodical Source Index (PERSI) - a comprehensive subject index covering more than 6,500 genealogy and local history periodicals written in English and French since 1800
* Revolutionary War Pension and Bounty Land Warrant Application Files with records of 80,000+ individuals who served in the Revolutionary War
This is the 6th most popular website used by professional genealogists, so I recommend trying it out. And if you are trying to sign on with your library card number, you first need to go to your library website and click on HeritageQuest from there to sign on. (I went straight to HeritageQuest Online and it asked me for a username and password; there was nowhere to put my library card number)