JUMP math - the online JUMP math site which explains the program and has downloadable materials.
AAA math - online site for math fun and practice.
Mathletics - curriculum and live math practice with avatars
Cool Math 4 Kids - online games to improve math and logic skills
Funbrain - math baseball anyone
BBC - KS2 - math science and english games
mathFROG - math games and printable worksheets
Mathwire.com - a math problem solving website with word problems from all math areas of focus