A fascinating source of how people think is "Yahoo Answers", where
random people ask for help from other random people. There is a section
for science and a subsection for physics. (Just follow the links from
the yahoo homepage or try http://answers.yahoo.com/dir/;_ylt=Aq2JdGkZ9IzWHS3mGuRVKqP4xQt.?link=lis
t&sid=396545211 for the physics page directly.)
You can easily follow the progression of the semester, because most of
the questions seem to be from people who are too lazy to do their own
homework. The level of answers varies from excellent to clueless to
just plain wrong. It would be an excellent source for discussion - ask
you students "which answer is best, and why?". The questions could also
serve to help spot common problems and misperceptions by students.