Monday - Time (and Timetables)
http://www.maths-games.org/time-games.html
http://www.bgfl.org/bgfl/custom/resources_ftp/client_ftp/ks2/maths/timetables/index.htm
Tuesday - Algebra (Remember the custard and Homer Simpson?)
http://www.crickweb.co.uk/ks2numeracy-calculation.html (Try the Mission Algebra challenge)
Thursday - Rules of Divisibility
http://www.basic-mathematics.com/divisibility-rules-game.html