I do 9"x11" - or 24x30 as it's known in Europe. I don't do anything bigger, as I've run out of space for trays (my enlargers take up too much space). I have done 11x14's in the past by "swishing" them through the trays, and even one 24x32" with sponges...

But I ticked 8x10", since I mostly print 18x24cm, 8x10", 24x30cm...