Play and Learn Esperanto on the Web and your Mobile Device
Duolingo Esperanto is a free, game-like Esperanto learning system for Web and mobile devices that has taken off like crazy in the last couple of years. It is free and fun - and they put forth that 34 hours of Duolingo practice is equivalent to one semester of university-level Esperanto.
Duolingo's free Esperanto course is great for beginners and intermediate learners. It teaches you Esperanto from step one and plays like a video game - including the addictive part! The learning system is visually stunning with cartoonish graphics and photos to illustrate vocabulary and concepts and help you memorize them.
Most importanly, perhaps, is that it is quite fun and keeps you coming back for more learning. Thus, there is no lack of motivation to learn a language.
Duolingo Esperanto Apps
Duolingo offers free apps for learning Esperanto on iPhone, iPad, iPod Touch and Android devices.