I am not aware of any academy type courses available for free. There is, however, so much educational material on every conceivable subject available on the internet you'll never have time to read all of it.
Spend some time exploring Firefighter Nation, then visit sites like vententersearch.com, firefightersworstenemy.com, firefighterclosecalls.com, firecritic.com, IAFF.org, firehouse.com and respondersafety.com, just to name a few. FEMA offers NIMS courses online at Emergency Management Institute (EMI) if you have not done those already. I-100, 200, 700 and 800 are required of all responders.
Finally, check with your local and state schools to see what they're offering. Here in Texas the state pays all volunteer firefighters' tuition for just about everything.
Welcome to FFN.
I know the US Fire Administration has good training bulletins on their website. Otherwise, firefighterclosecalls.com has some pretty good bulletins as well. Forrest Reeder puts those up. Great instructor very knowledgeable. Many websites have things like that you can do. Also, another good one to try is fullyinvolvedfire.com. They have a command simulator for free, while very basic, will let you know where you stand. I will do some more research and get back to you if you like. The USFA website is http://usfa.fema.gov. Hope this helps.
I know in the State of TX they had a website for the Certification Curriculum Manual approved for NFPA FF I&II that is what I have been studying from I find it very helpful!
It has all the curriculum to pass the test you just have to study and find the answers yourself but it's worth it you learn. if I can be of any help let me know I am not a FF but I look everywhere to try and learn the most I can before I test for my civil service this summer.