At the Martin Mere wetlands centre in Lancashire last weekend I saw an enormous puffball fungus. I don't know if you can see the pine cone at 2 o'clock in the photo for comparison but this thing was huge! Easily 18 inches across.
I've tried eating the giant puffballs that grow in the woods around here. They're best when about tennis ball size, but I find they don't have a lot of flavor. They smell wonderful when they're frying, though! My pic was taken in August 2008.