U.S. Code of Federal Regulations (CFR). Available in Nexis Uni.
Federal register. Available in Nexis Uni.
The Government Printing Office hosts an electronic unofficial ( and thus not considered legally binding) version of the Code of Federal Regulations here. It is relatively easy to browse through the various sections. Similarly, the GPO hosted Federal Register is here.
New York Code, Rules, and Regulations (NYCRR) Available in Nexis Uni.
Unofficial version available on the New York State website.