If you are in the process of trying to trace your family history, there are a number of great geneaology resources online that will allow you to search for information about your genealogical history. 

First, check the National Archives for census data that goes all the way back to 1790. The National Archive has a free search function, there are also links to services that you subscribe and pay to use. You can also find information on Native Americans, veterans, and much more using this site. 

Another great site is the National Center for Health Statistics. You'll have to have some basic information on your ancestors to use this site - such as birth date, date of marriage, date of death, state of residence, etc. It's an invaluable resource to find more information about your ancestors once you've put together the basic information. 

Access Geneaology is another website that you can use in your search.  It's free and provides a lot of good information for those who are searching for geneaology records.  

You may still end up using a paid service to trace your family tree, but there are plenty of free resources that will help you on your search.  Finding geneaology records is a great family activity especially if you have pre-teen or teenage kids as they can assist with the research.  It's a wonderful way to learn about your family's history and to get your kids involved in something on the internet that is actually productive!  We've recently started trying to put together our family tree and my 13-year old is actually enjoying helping with the research and finding information.