The Arcademic Skill Builder site is WONDERFUL and FREE! Great drill and practice activities for both Language Arts and Mathematics.
Especially cool are:
New Multiplayer Games - you can practice your Division (Drag Race Division) and Multiplication (Grand Prix Multiplication) skills against other players around the world or your friends!
Wii Formatted Games - check them out here: http://arcademicskillbuilders.com/wiilist.htm