This website, which lets people design their own rooms is frickin awesome.
Once you get to grips with the intuitive control system (and your ancient laptop stops crashing), you can have a cracking looking room created in ten minutes, with the option for different views. The really nice thing is that the 3D view looks best, but the plan view allows you to get the measurements added on as well - in the words of Stinson, Legen-wait for it.......dary.
Having made our rooms, i was then able to provide people with a couple of shopping websites, asking them to buy the carpet, enough paint to cover the walls, and skirting boards long enough to go around the room. They were then allowed to spend whatever money they had left on furnishings (note to self: all kids want to buy a 8 bajillion pound flat screen TV if given the chance, even if it means living in a cold baren room). Kids who had struggled with ideas of area and perimeter suddenly thought it was the most obvious thing in the world, although some of them struggled to price things up (one group said they needed to spend £4000 on paint...)
As a functional exercise in why they might actually need to understand area and perimeter & why they might need to understand simple ratios (eg 1 tin covers 4 square metres, my room is 20 square metres...) it was hugely entertaining diversion from what it generally a very dry topic area.
Next up, Project: Plastic surgery, where we investigate how to make ourselves look like Brad Pitt on a budget of £24.35.