I see the "Where do atheists get their morals from?" question has appeared. Anyone who's ever gotten into internet arguments (on the appropriate forums) will feel their shoulders slump a little when this is raised yet again. So, here goes...

I get my morals from wanting to live in a society that works. A society where everyone does whatever they want? That doesn't work. It would quickly self-destruct.
A society with reciprocal acts (the "Golden Rule") works.
Just think it through: I don't want people to murder me and/or steal my stuff. Therefore, I expect they wouldn't like me to murder them and/or steal their stuff. Therefore, we mutually agree (tacitly or by writing explicit laws) not to murder each other and not to steal each others' stuff. This is a sound and sufficient basis for creating a moral system.
What I don't require is someone watching over my shoulder with a big stick and threatening to hit me with it for any bad things I've done when I've completed my alloted time alive. Living under that system means I act good only out of a selfish fear of pain/hurt, and not because I know acting morally is an essentially good thing to do for improving the society I live in.