I think it is very mis-leading to say that for humans
evolution has stopped. Humans definately have the
ability to adapt culturally and behaviourly which on a
surface level seems to negate any selective pressures
of the environment (ex. changes in temperature).
But we do not need to look much farther than the turn of
the 20th century for evidence of selection on the human race.
In the first two decades of this century a great flue
epidemic had swept the world. Many millions of people
died. This was a very hard dose of selection. Only those
that had an immune system capable of fighting the disease
survived, and thus past this trait on to their offspring.
So although it seems that we no longer evolve, we may
actually be evolving in subtle ways that we often overlook.
As well there is the chance that we may evolve in ways
we cannot imagine or forsee. It all boils down to the nature of
DNA and DNA repair and as long as we share the same
"nuts" and "bolts" of heredity with other organisms we
will continue to evolve.