Duolingo is a free tool, and it makes language learning a game. It’s available in many languages, and is really fun! By far the best free resource there is.
The BBC has tons of free language learning resources available online.
TPRS is a method of language instruction called Teaching Proficiency through Reading and Storytelling. I am a huge believer in this method. It focuses on learning by actively participating in conversation and storytelling, both by speaking and by acting out the stories being read. My German and Mandarin Chinese teachers both used this method, and I learned so quickly I couldn't believe it!