Education Quizzes offers a wide range of quizzes on a variety of topics. It is American in its content, but science crosses all borders.
This tool should be used as a supplemental tool and for practice quizzes. It requires payment to have an account, but the quizzes can be used without logging in.
Wolfram Demonstrations offers over 12,000 demonstrations and simulations for everything from advanced science and physics to K-2 science to arts and architecture. There is something for every teacher on this site!
iPractice Math uses game based principles to encourage students to learn through discovery, they also have all the usual stuff schools may like such as worksheets, lesson plans, and of course real time reporting.