Hi Captain Cadet,
Some sites I've used in the past:
GCSE Bitesize (BBC)
Sam Learning (Or any other site that your school has got a paid account for).
S-Cool(.co.uk)
* My Maths (Maths only, obviously).
Even Youtube can have some good stuff on it, if you're looking at particular subjects like History or Geography (Although if you're year 9 you won't be doing your options yet I take it?)
And of course you can't forget the good old fashioned text book...
Good luck!
Jack.