1. General: The Building Codes and Standards page at the website of the National Roofing Contractors Association is a good place for up-to-date information about building codes and how they affect roofing.
2. General: An excellent one-page explanation of the roofing section of the 2012 International Building Code. From the November 2012 issue of Professional Roofing magazine and archived at the website of the National Roofing Contractors Association.
3. General: Select your state on the home page of the Building Codes Assistance Project (BCAP) for state code information. On this site you can find information regarding code status, guides to building codes, and more. The focus is on United States jurisdictions, but some useful international information is available as well.
4. General: To view actual building codes, plumbing codes, fire codes, etc., (check the website of your local building inspector's office to find out which code is currently in effect in your area) see UpCodes. For example, see here for a look at the roofing section of the 2015 International Building Code. See here for a look at the roofing section of the 2015 International Residential Code.