Internet links to government agencies, statutes, regulations, cases, etc. are posted by FindLaw and WashLaw. Primary legal materials are also available from Lexis and Westlaw. Google Scholar has free cases back to 1950. Supreme and appellate court cases are published in the North Eastern Reporter.
The Illinois General Assembly posts the Illinois Compiled Statutes, Public Acts since the 77th Session (1971-72) and Bills and Resolutions since the 90th Session (1978-79).
To check on the status of pending bills, pull up the bill page on the Legislation page of the General Assembly web site and scroll down to the "Actions" seciton. For questions, call Legislative Information System at 217-782-3944.
For a summary of Illinois law, see Illinois Jurisprudence (ILL;ILJUR on Lexis) and/or Illinois Law and Practice (IL-LP on Westlaw).
For a discussion of Illinois legal materials, see
Illinois Legal Research by Mark Wojcik's (Carolina Academic Press) or the Illinois Legal Research Guide by Laurel Wendt (William S. Hein & Co.).
For questions about Illinois legal materials, copies and/or inter-library loan, try calling the D'Angelo Law Library at the University of Chicago (773-702-9631) or the Pritzger Legal Research Center at Northwestern Law School (312-503-8451) or the University of Illinois College of Law Library (217-333-2914).
Legal Data Resources (800-735-9207) specializes in document retrieval from Illinois courts, government agencies, etc.
The Digital Session Laws Collection on HeinOnline has Illinois session laws back to 1809.
Legislative History: A good guide to Illinois legislative history research is posted by the Pritzger Legal Research Center at Northwestern University. Links to other guides are posted by the University of Indiana at Bloomington. Note: Illinois revised its statutory code in 1992 and changed its name from the Illinois Revised Statutes to the Illinois Compiled Statutes.
Practical Tip: For bills since the 2000s, everything is available free on the Illinois General Assembly website except the recordings of committee meetings. Recordings are available for House Committees starting in the mid-1970s (call 217-782-8100 to order) and for Senate Committees starting in 2012 (call 217-782-5715 to order). Also: You can search all of the available legislative history materials starting with the 91st General Assembly (1999-2000) with Westlaw's IL-LH database.