There is an interesting essay on Rights on this page. Here's a little bit of what it says:

One of the most important and influential interpretations of moral rights is based on the work of Immanuel Kant, an eighteenth century philosopher. Kant maintained that each of us has a worth or a dignity that must be respected. This dignity makes it wrong for others to abuse us or to use us against our will. Kant expressed this idea in a moral principle: humanity must always be treated as an end, not merely as a means. To treat a person as a mere means is to use a person to advance one's own interest. But to treat a person as an end is to respect that person's dignity by allowing each the freedom to choose for himself or herself.

Kant's principle is often used to justify a fundamental moral right, the right to freely choose for oneself, and rights related to this fundamental right, sometimes called negative or liberty rights. Negative rights, such as the right to privacy, the right not to be killed, or the right to do what one wants with one's property, are rights that protect some form of human freedom or liberty, . These rights are called negative rights because each one imposes a negative duty on us--the duty to not interfere with a person's activities in a certain area. The right to privacy, for example, imposes on us the duty not to intrude into the private activities of a person.