A common attack on atheism is that without God there can be no morals.

This argument assumes that morality can only come from God - that human beings are unable to determine any type of moral code. It also seems to assume that people only know something is wrong because God decided it to be so.

It is entirely possible for a person to come up with a moral code without needing to look toward religion to dictate what it should be. One good starting point is respect for others - assuming that all people have the same rights, and not assuming yourself as the most important person there is. Once you've accepted this, then it is possible to determine what you should and should not do to others based on equality.

Morals without a religious source are also able to change when society changes, discarding useless ones and adding new useful ones.

Anyone can have morals. In a totally decentralized moral universe, morals are like assholes - everyone's got 'em. But humans are imperfect. They can't make a perfect OS, a perfect government, a perfect anything. Anyone can have morals, but "For that which I would do, I do not. That which I would not, I do" (Romans 7:19) - there is still the need to follow through on whatever belief system you have, whether man-made or one untouched by human hands. Good luck, either way.

In god(s)-based religions, morality is just another commandment from god(s). If one is not moral, they are punished in some form or another, ranging from a less-than-great harvest to eternal fire and brimstone. This drags morality down to the level of the lowly pleaure-pain principle.

Morality out of fear of punishment is repugnant to the concept of morality.

Those having difficulty with the concept of an atheist with morals might benifit from a good look at their own. If your only reason for not raping children is "God(s) probably wouldn't like that...," you have some soul searching to do...