Apps are your place for fun vocabulary practice. There's no shortage of courses in almost every language you can imagine—or invent, as there are also several courses on constructed languages—created by a vibrant user community. You can find standardized courses based on popular textbooks or vocabulary frequency lists, as well as less-expected vocabulary collections.
The apps follow a learning method that is based on creating funny or quirky associations with the words being learned. You can follow other students and compete against them for points, and see how well you are doing in the rankings for a particular course. It is very motivating to surpass others!
Apps can help with grammar, suggest additional resources, and even assign and correct homework for those who are interested.
Courses are broken into small 10-15 minute sections to keep things interesting and ensure you have enough time to study a little each day. They also use an algorithm that tracks your progress throughout the course, so your review topics are tailored exactly to your needs.