Heritage Quest is a business that sells lots of genealogy CDs, magazines, books, microfilms and other software. You can join their "Research Club" (which does not include online access, but does give discounts on merchandise) for $29.95 per year. They claim to have all sorts of source documents, including immigrant ship lists, Native American data, state data, etc., including local histories. You have to join through Genealogy.Com to access their online databases of all the Federal Censuses (including the existing fragments of the 1890 "lost" census). I do not know the cost of all that. HOWEVER, if your local library has a website, check to see if they have any "Online Research Sites", either accessible at the library or from your home computer. My library card gives me a password to access Heritage Quest from home--for free! (I can also access Ancestry.com from the library computer, but only Heritage Quest can be accessed from home.) This means I go first to the library website, then to Online Resources, a library card number and password is required (which gives me a password to enter the Heritage Quest online database) and eureka! I have found the census images to be quite good, for the most part, but since they are images of the originals, you have to deal with someone else's handwriting and spelling. They have some of the census indexed: 1790, 1800, 1810, 1870, 1890 (fragments), and 1910, but all of the censuses are browsable. They also have some books online, both family histories and local histories, searchable by "People", "Places", or "Publications." I have not ventured into this part of the site very deeply, as I tend to concentrate on one source until I think I have all the data available, before moving to another.
For example, using "Illinois" in the search box brings up 21 books (which can be read online), ranked by their relevancy rating system:
History of Wasco County, Oregon
An illustrated history of the counties of Rock and Pipestone, Minnesota
History of Iroquois County Watseka, Ill.
Iroquois County Board of Supervisors, 1968
Genealogy, Napoleon Senesac family
An illustrated history of Spokane County, state of Washington
An illustrated history of Umatilla County Spokane, Wash.
Illinois activities in the World War : covering the period from 1914 to 1920
History of Cherokee County, Kansas and representative citizens
History of northern Wisconsin
History of La Salle County, Illinois
History of the early settlers of Sangamon County, Illinois : "centennial record"
The History of Contra Costa County, California
Portrait and biographical album of Rock Island County, Illinois
In the foot-prints of the pioneers of Stephenson County, Illinois : a genealogical record
history of the city of Vincennes, Indiana : from 1702 to l901
Memorial and biographical history of Dallas County, Texas
Counties of Warren, Benton, Jasper and Newton, Indiana : historical and biographical.
Past and present of Washtenaw County, Michigan
A history of the Robinson and Hawley families : (including findings on the Morris, Putnam, Cary and Plummer families)
Family record of James Carse, Sr., 1793-1846, and his descendants
Genealogy of the Child, Childs, and Childe families : of the past and present in the United States and the Canadas, from 1630 to 1881
Some of these books may only mention Illinois and some may have been published in Chicago, so you have to go through the lists to determine if any of them might pertain to your research.
Would I pay for access to this site? I doubt it, even though the census images are easy to navigate and the quality is, all things considered, good. Do I use and enjoy it? Yes, very much so. Would I recommend it? If you have a lot of census searching to do, it might be worth your while, depending on the price. I like the convenience of doing my research at home. Heritage Quest does not have all the other databases on line that Ancestry has, so if census research is only a small portion of what you are looking for, it probably is not for you. I must mention, also, that there has been very little "downtime" since I have been using this site. They do have some sort of "maintenance", but it is performed after midnight, and only once (about 3 AM) was I unable to access information. This could be attributed to the library website as they are doing some updating and making changes to the catalog.