I used to think "Rule 4....BORING....I know what this stuff means." But since I have been on this site and become a little more of a student of the game, I've learned that Rule 4 is huge. Simple terms like "Player" vs. "Bench Personnel" or "live ball" vs. "dead ball" may seem easy enough on the surface but you need to understand them (and others) to really understand how the rules work. I think this is also why most basketball official classes start with Rule 4 rather than Rule 1.
Back to your question, there isnt too much NF sponsored stuff online past their web site which is
http://www.nfhs.org
Unfortunatlely until the Fed thinks its more important to get information out to more people faster rather than generate book income, you wont see anything worth while online.