My American colleague, Mrs Laguna, is also a member of Quia, where you can create any of thirteen different activities (from battleship to scavenger hunts), as well as quizzes and surveys. As well as creating your own activities, as a member you can browse the activites of other teachers.
Here are a few for my year 9 Science class to try:
Electricity and Magnetism – Who want to be a Millionaire?
And for year 7 Maths (decimals, fractions and percentages):