If you’re interested/have any prior proficiency, you can take Headstart2 language courses through ATTRS. I’m taking the German and Russian courses currently to maintain my proficiency. If you check out the Defense Language Institute Foreign Language Center and go to “Online Resources” under the “Resources” tab, it’ll have a link to their Headstart2 page and you’ll be able to find all of the available languages and other information. Aside from that, I’m hoping to get input from others as well to help expand my knowledge base.