That's the defeatist attitude that Kerry and Bush are banking on. This is what the two party system has done to the national psyche, the elephant teathered with twine. Have some courage, don't be a sheep. Vote for guy who you actually want to be president. That's how the system is supposed to work.
Imagine if all the voters who have the same sentiment as you really did "throw their vote away" on a third party candidate. That might even be enough votes to win, nevermind making the party stronger for 08.
In my opinion if I voted for Bush or Kerry I really would be throwing my vote away.