You will find many games and puzzles to try here (all free!)
You may like to try the following to start, these games are easy to understand and use.
Click guest and then any of the sample games (green tick beside game). Sample games are available in all the categories. Note that the free games seem to change all the time so you can try a good variety. Play at your chosen difficulty level – games available for Algebra, Data, Number and Shape.
Available on Math Playground, the 25 levels of Think Outside the Flock will test your thinking skills!
Can you make these little people all stand up in the Mathisfun RayRay game?
If you want to practise your tables there are many sites to help you; try some of the suggestions here.