http://www.bbc.co.uk/bitesize/ks1/maths/ - games 

http://www.crickweb.co.uk/ks1numeracy.html - games

http://www.topmarks.co.uk/Interactive.aspx?cat=8 - games (tablet friendly)

http://nrich.maths.org/primary-lower - Lots of problem solving 

http://www.ictgames.com/resources.html - games