CyQuiz is a free site that allows you to create quizzes and games. You do not need to signup and it works in your browser (no Flash required). It works on Windows, Mac, iOS, Android and Windows Phone.
There are existing quizzes you can use or you can create your own quizzes. Quizzes can have pictures and sound in them and you can create multiple skill levels in the games.
There are game templates and the games are great for helping students learn concepts while having fun.
It's free, easy to use, and a great way to create some quizzes and games for your students. You can also have students create games and quizzes as a class project. The site also has tutorials to help you.