1. General: For a good, informative general article about various roof systems, see this page at the Whole Building Design Guide site, which is maintained by the National Institute of Building Sciences.
2. General: "How They're Made: CertainTeed Asphalt Shingles" is a two-minute video that quickly covers the manufacturing process for asphalt shingles. It's kind of fun to watch. Reminds me of the educational films they used to show in elementary school.
3. Building Codes: "R905.2 Asphalt Shingles" from the 2015 International Residential Code and "1507.2 Asphalt Shingles" from the 2015 International Building Code. Both available at the UpCodes website.
4. Hail Damage information/links can be found on the Roof Online Hail Damage page.
5. Inspection: "Mastering Roof Inspections: Asphalt Composition Shingles, Part 1" at the International Association of Certified Home Inspectors' website is a good place to start. There are 54 MORE PARTS (!) in this asphalt shingle roof inspection guide, and they can be accessed from this page. Anyone who has an asphalt shingle roof should take the time to look through this guide. It's more like an owner's manual than an inspection checklist.
6. Inspection of asphalt shingle roofs: "ROOFER: Steep Roofing Inventory Procedures and Inspection and Distress Manual for Asphalt Shingle Roofs" is an extremely detailed and valuable resource put together by the US Army Corps of Engineers' Engineer Research and Development Center, and available for download at the Defense Technical Information Center website.
9. Technical: "Blistering of Asphalt Shingles" is a short technical bulletin available at the website of the Canadian Asphalt Shingle Manufacturers' Association.
10. Technical: "Installation of Asphalt Shingles on Low-Slope Roofs" is a technical bulletin from the Canadian Asphalt Shingle Manufacturers' Association. Provides guidelines for installing shingles on roofs with slopes between 2/12 and 4/12.
11. Technical: "Wind Effects on Asphalt Shingles" is a thorough, well-sourced, and well-illustrated technical paper made available by Haag Engineering. Gives you a good understanding of the subject, and helps with identifying wind-related roof damage.
13. Manufacturers: For a list of asphalt shingle manufacturers, see here.