Law libraries and law librarians are committed to fostering legal knowledge and thus create guides for legal research, subjects, and processes. These guides are usually freely available for anyone to view on the web. Most all law schools contribute to this effort under the LibGuide system, so searching for your desired topic + "LibGuide" into your preferred search engine can be worthwhile.
Directory of online resources for each U.S. state and region, as well as the U.S. federal government and Canada, with potential for additional information about the sources themselves, access, citation, etc.
Collections of guides for all types of legal topics with recommended resources online and amongst the Law Library's collection itself. For those very new to legal research, the LLC has a collection of Beginner's Guides.
The Illinois Supreme Court provides subject guides, civil appeals research guides, and a guide to how to conduct Illinois legislative history.
The University of Illinois College of Law has subject guides, research guides, and guides to accompany particular classes.