Everyone as pretty much said all there is to say on the matter, but I just wanted to add my personal opinion. I just refuse to believe that any self-conscious being completely ceases to exist when they die. To have it so would make all of life pointless IMO, because even if you do good in your life, then all you did was affect others who are doomed to not exist in the near future. In the greater scheme of things, each individual's death is meaningless, therefore whatever you do in life is also meaningless.
I guess what I'm trying to say is that if we all live to eventually die, and then be gone completely, then there is no point to life at all. We may as well as just nuke the planet so that no one ever has to suffer any more. Anything we could ever do on our tiny, insignificant planet won't affect the universe, or probably even another solar system, so why put the effort and suffering of trillions of lifeforms through life's problems. That's why I do believe in something after death. If there is something to exist for, then maybe we can make a difference in the grand scheme of things.