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. Hail Damage information/links can be found on the Roof Online Hail Damage page.
3. 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.
6. Technical: Blistering of Asphalt Shingles is a short technical bulletin available at the website of the Canadian Asphalt Shingle Manufacturers' Association.