When preparing my daughter for her 11+ I typed up questions and answers about all the important things she needed to know (list of prime numbers, formula for finding area of a triangle, how many metres in a kilometre etc) then laminated them.  I got her little sister to test her on these in the car – they both really enjoyed this and she got the facts learnt.  Making posters about all the maths facts they need to learn is also a great idea - break out the glitter, tissue paper, glue and gel pens and let them be as creative as possible!