This article is from the storage FAQ part1, by Rodney D. Van Meter with numerous contributions by others.
This area moves WAY too fast for me to keep up with all of the products and announcements; ideally, it should teach enough about principles and other information sources to allow users to find the information they need. Quantum has a good educational web site, with info on the history and technology of disk drives, at http://www.quantum.com/src/storage_basics/toc.html. A lot of spec sheets for recent disk drives (when they say they also have "old drives", they mean early 90s, not 50s-80s) is available at http://www.blue-planet.com/tech/index.html. Looks like a good site.