Spy Guys lesson and game.

Mixed Numbers game.

Each correct answer donates rice through the United Nations World Food Programme.
Do some multiplication facts!!! http://freerice.com/#/multiplication-table/17478

Place Value challenge! Choose "Super Brain" level! http://www.funbrain.com/tens/index.html

Decimals of the Caribbean! http://mrnussbaum.com/docrb1/

"Make 24" - a challenging game where you re-arrange numbers and operation signs to make an equation that equals 24. 
http://www.sheppardsoftware.com/mathgames/make24_level_one/make24AS2_level1.htm

A kooky game where you have to find multiples of a selected number. Please challenge your brain and pick multiples of 4 or above! http://www.mathplayground.com/multiples.html

Place value game: http://www.321know.com/g41a_px1.htm#section2
Jefferson Lab place value game: http://education.jlab.org/placevalue/index.html
           -> Select from 6 to 9 digits
           -> Select 9 as your largest digit
           -> Select ZERO discards! (Challenge yourself! You can do it!)