In my opinion, you should vote for a third party--and encourage others to do likewise--because if we ever get a third party in office, it would send a dramatic message to the Republicans and Democrats that their days of running the show are over. I can dream, can't I?
They say that third parties are "wasting your vote," but I think you are wasting you vote if you choose either the two main candidates. Plus, with lower voter turnout, your and your friends' votes have greater weight.
wombatron:
I'll probably just write in my cat Leonidas 
I love cats!
"We have thus stepped back from the position our ancestors occupied; for we allow under the flag of justice, and consecrate in the name of the law, what was imposed on them by violence alone."