Well I just want to say that I put aside my Wii playing and took the time to vote. So if this American living in the UK can take time to do it, the rest of the lazy, over 18 year old Americans can do the same.
Milky - I don't know how long it takes in most states, but where I'm from (Washington State) we have the option of voting by 'absentee ballot'. We can opt to get our voters ballot via the post, and sent it back or drop it off when we've filled it in.
I know in some states they are opening the polls already so people can start voting now. I don't really think there's a lot of excuses for people who don't/can't/won't vote.