There are several low- and no cost online options for both the United States Statutes at Large and the United States Code. Below are links to sources for federal statutes. If you do not have a citation for a statute, several of these sites offer indexes. For information on conducting statutory research, see the Statutes & Constitutions Research Guide.
The availability of state statutes and codes vary greatly. In many instances, they are published by commercial publishers. Many states also publish their statutes on their legislatures' websites. Some states may have official and unofficial versions of the state code, others may only have one version. Find the exact title of the state's published code and session laws from table T1 of the Bluebook.
It is important to remember that not all websites keep information up to date - please double check the information before relying on it. The links below are to sources that are generally regarded as reliable.