WarGameVault is a business for gamers, of which I am not (gamer, that is). But I've occasionally found stuff of great interest to me on the subjects of history, war, etc. of which I do have an interest.
You might be interested in knowing that they currently have 879--don't adjust your monitor, that's 879--free products. I assume that all of these are digital products, because, well, that's all that they sell.
You might want to give a look-see at this selection. Thankfully, there is a filter, so that you don't have to go through the entire selection to find topics of interest to you.
http://www.wargamevault.com/browse.php?pto=0&pfrom=0.