(legislating morality is ) Passing laws that tell people what they can or cannot do.

Correct me if I'm wrong (and I'm sure you will), but don't all laws tell people what they can or cannot do? A law that doesn't tell anyone to do or not do anything is a waste of paper.

So, I guess the real question should be, what laws legislate morality, and what laws do not?

The government is then supposed to enact laws that prevent citizens from infringing on the rights of other citizens, and punish those that choose to do so.

That sounds fair to me. But what sorts of activities could infringe upon the rights of other citizens?

laws against public nudity, gun control, age of consent, drinking age, drug laws, voluntary euthanasia legislaton

You're right. A lot of the above examples do seem to have no bearing on any other individual, and I would agree with you in saying that they are probably an example of the government overstepping its bounds. However, what is the purpose of gun control if not to prevent me from shooting you? Age of consent laws prevent adults from manipulating and sexually exploiting vulnerable adolescents. Although I believe each person should be allowed to choose his or her time of death, voluntary euthanasia and assisted suicide are a slippery slope that could lead to doctors and family members pressuring the terminally ill to die faster.

Personal freedom is a very important and valuable thing. But when you enter into a social contract, you accept the some limitations in return for all the benefits awarded to you as a member of society.