iGrow
Reading Jo Boaler's "Mathematical Mindsets" led me to create this activity. The latter part works well with pupils taking it in turns to come up with a different Growth Story.
Hexominoes
Martin Gardner's Pentominoes have been so popular that I decided to add a 6 tile version!
Four Fours
An old favourite - using four fours and basic arithmetic to generate the first ten numbers.
And here are some interesting follow up ideas.
Bits
A very friendly and fun introduction to how computers do their stuff.