Nate Silver, Andrew Gelman and Aaron Edlin Have written an article about the probability of your vote making a difference in the electoral outcome based on the state in which you cast your ballot.
One of the motivations for voting is that one vote can make a difference. In a presidential election, the probability that your vote is decisive is equal to the probability that your state is necessary for an electoral college win, times the probability the vote in your state is tied in that event. We compute these probabilities for each state in the 2008 presidential election, using state-by-state election forecasts based on the latest polls. The states where a single vote is most likely to matter are New Mexico, Virginia, New Hampshire, and Colorado, where your vote has an approximate 1 in 10 million chance of determining the national election outcome. On average, a voter in America has a 1 in 60 million chance of being decisive in the presidential election.
While I like this as a academic exercise the possible message scares the hell out of me. The message being if you live in a deep blue state, say California or New York that your vote will not really make a difference in the ultimate outcome. If the lines are long or something else come up it's OK to bail because Obama is going to carry the state anyway with or without you.
Folks while numerically this may be true. Please stop and consider this counter argument.
This year the popular vote matters more than ever. The Republican party has come very close to destroying this country. We as moderates, progressives, Democrats or Independents need to send a clear and unambiguous message to the Republicans. The message, in your present form as a Party you are done, finished, kaput. And if you ever want to have a place in American politics or government again you need to spend some serious time in the wilderness rethinking what it is you stand for. In order for this to be accomplished there not only needs to be a resounding EV defeat, but an equally resounding popular vote defeat.
So don't any of you think that because you live in a safe state your vote doesn't count! It does, now more than ever! I don't care if the line is eight hours long, stay in it. I don't care if you get hassled about your ability to vote as a last resort fill out a provisional ballot. Just make sure you vote!