Math-play.com has links to great math games! There are games for every level so older and younger siblings can enjoy as well!
Mathgames.com has a great selection of fun math games about fractions!
Gamequarium.com has games for all subjects! There is a nifty page all about fractions!
Mathplayground.com has a great variety of fraction games! The games can be set to any level so there is something for every type of math learner!