Some interesting articles I found on the positive effects of smiling and laughing:
It helps pregnancy, for one!

:
http://www.grenswetenschap.nl/permalink.asp?grens=454There are some serious health benefits:
http://helpguide.org/life/humor_laughter_health.htmAlso, it is extremely contagious, so start spreading some joy!

:
http://positivepsychologynews.com/news/emiliya-zhivotovskaya/200809271036Unfortunately, some people CAN'T smile! How sad...

(Luckily they are capable of experiencing internal joy):
http://en.wikipedia.org/wiki/M%C3%B6bius_syndromeIf you find anything interesting on the subject, or just have a really good joke

post it here!