My girlfriend here at the University of Wisconsin told me that she was

studying at a campus library one afternoon during exam week, sometime 
around May 12 give or take 3 or 4 days either way, and saw a strange 
object flying over Lake Mendota.
She said the object was shaped like the cross-section of a regular boot 
would appear.  It didn't appear to make any strange flight patterns or 
have any lights, especially since it was daytime, but the boot was 
receding somewhat quickly away from her view.  A woman studying across 
from her noticed the object as well, and both agreed it was strange.  
They ruled out a blimp, weather balloon, helicopter, and airplane.  Since 
it was already quite far, it was difficult to make out any particular 
coloring or other surface pattern.