Slate has the best article ever on not voting.
Even for the most passionate partisan, it's hard to argue that voting is a good use of your time. Instead of waiting in line to vote, you could wait in line to buy a lottery ticket, hoping to win $100 million and use it to advance your causes—and all with an almost indescribably greater chance of success than you'd have in the voting booth.
(They give equal time to the counter-argument, of course.)