The concept of place value in Maths is one of the key building blocks, without which a child will struggle with many other skills. Most schools make creative use of hundred squares to help young children to become fluent with the first hundred counting numbers. For some reason, nobody goes any further than that and result can be a real nervousness around larger numbers.
Some time ago, I met a 14-year old who had a very poor understanding of larger numbers. In her lesson, I built a very simple computer game to help her explore them. Over the following 2 years this developed into a suite of interactive computer games which I play with new students if I suspect this may be a problem for them too.
I also created a simple board game which students can play to help them get to grips place value.
Both computer game and board game are available to my private students in lessons and as homework.