Lingopolo is a free website designed to teach you to understand and speak languages. It does this through online lessons taught through quizzes.
For example, here is an example of a multi-choice question:
You can study the language with dozens of different themes:
Every theme breaks the subject down into a series of easily-digestible courses:
When you complete a particular course, you are rewarded with the next course being unlocked.
Every Course follows the same structure: on the left you have a lesson with 10 words and on the right you have an Examples lesson with phrases to practice the words:
Each lesson shows you how you're doing in progressing through the lesson:
Your home page allows you to track your progress over time. This helps too to keep you motivated as you look back upon how far you've come: