Four years ago I "sat out" the presidential election, voting as a Green for its candidate, Ralph Nader. (Fortunately, California was a "safe" state that went solidly for Gore, so I didn't end up losing sleep over my vote--and in fact, at the time, I regarded the choice of Bush/Gore as a tweedledee-dum situation.)
This time, I voted as if my vote counted, even though Kerry was a lock in California and I wasn't enamored of his candidacy much.
Now, if I were a Sunni Muslim in Iraq, what would I do? One Imam calls for a boycott, others believe participation is imperative. This article spells out their dilemna, and for them the stakes are as high, if not higher, than ours were in 2004.