Where's the # key in Lion In Snow Leopard alt-3 used to print a #, in Lion it doesn't. 
I'v tried different key combination keyboard viewer but still no luck.
Any ideas were the # key went?
Since it varies by keyboard layout - why not open your keyboard viewer and find out?

In the US keyboard layout on lion, it's still shift + 3



You have to select this from the menu bar after enabling it in the menu bar