Illinois has a relatively deep collection of legislative materials hosted on the Illinois General Assembly's website (ILGA). You can use the ILGA website to find copies of proposed bills, track legislation, look at historical materials, find transcripts from floor debates, and sometimes to locate other materials from committees and hearings.
Note: a full legislative history is only available if the law is from after 1971. IL had a completely different system prior to 1971, and a full legislative history is not able to be constructed from those documents.
UNDER CONSTRUCTION: this area to be populated with a state-by-state resource list.