http://www.sd22.bc.ca/silverstar/writing/mysteries/mysteries.html
an archive of the sort of thing you’re looking for,

http://www.qesn.meq.gouv.qc.ca/schools/olp/2mmclub/solve.htm
“The 2-minute mystery writing club” I didn’t browse through the ones
listed; they’re written by school children, but that doesn’t really
mean anything about the quality…

http://www.qesn.meq.gouv.qc.ca/schools/olp/2mmsolve/current.htm
Same organization as the above, but these seem to be from anybody who
wants to submit.

http://www.transformationalthinking.com/html/two_minute_mysteries.html
Don’t know what the group behind this page is about, but give it a
try.

E-Mail from Barbara Bailey