Anyone Seen Evolution?

[Jeff Bush]

I recently saw on the news a group of mutated frogs (most likely occured 
from the waste we produce).  These frogs were surviving, but these 
mutations didn't seem to improve the frogs any.  So I was just 
wondereing...
 
Has anyone ever observed a true *benefitial* mutation occuring in nature?

And by the way, don't give me examples of Natural Selection, I know the 
difference.