Old folk like me will probably remember the National Numeracy Strategy (NNS) Interactive Teaching Programmes (ITPs) – some of which were great and some of which were horrible.
It turns out, they were great tools to show loads of mathematical ideas on whiteboards – but because they were made in the late 90s, and in Flash, lots of them no longer work.
Ted Burch of mathsframe.co.uk has very kindly remade them all in html5
The reworked programmes should work on tablets and most modern devices.
There are currently 25 remade tools which are all available for free here: