To start our work, and to quickly help beginners entering intermediate and advanced matter understanding, we already received good suggestions, as the use of good books.
I fully agree, and I let my American colleagues going on with suggestions.
-because I'm Italian, I've very good books all in Italian! I need then to base my work on some easy-to-find English resource.
-because this Academy is free, and is based on the web big opportunity, I suggest to base our work on wonderful already existing web sites and free software: the requirement for the resources is evident
TO BE TOTALLY FREE: free of charge and fees, free access, freeware license.
( simply because everybody can use it as a reference, even if doesn't want to buy or to pay for it. To buy software or hardware services and media, should be only a personal choice)
ABOUT COPYRIGHT: be careful please. Freeware and free access web sites are anyway copyrighted, then don't copy and don't modify proprietary content if you want to share it.