 One of my favorite free software is a project called Anki. It's a free software licensed by the AGPL and it's flashcards for learning. So I use it to learn languages like German and as an immigrant living in Germany, I find it very useful to use it almost every day to improve my vocabulary and to improve my grammar. I'd like to say thanks to the developers of Anki for making such an effective learning tool and that's also free. Thank you.