SensibleUnits.com is essentially a conversion site, but rather than converting inches into metres it will convert such things as 1 England, or two AA batteries end to end. For example I entered my height and discovered that I was equivalent to 6.9 average footballs, or 1.1. Alaskan moose antler spans. Lots of fun, but is it useful? I think it could be very useful for helping to visualise what a unit of measurement is worth, for example one metric tonne = 1.3 cows. You can also put countries, planets, counties etc. into the lefthand side and see what they are equivalent to, thus 1 Yorkshire = 3.3 Cornwalls.