The Susan Lee piece on libertarianism that Tim cites is welcome, but I think she pushes the moral relativism angle a little too hard. Libertarians may not want to impose their moral judgments on others (beyond enforcing the basic rules necessary for peaceful coexistence), but that does not mean they have none. The political philosophy is compatible with a wide range of moral views on matters such as marriage, sexuality, drugs, and popular culture. It just requires that force not be used to promote those views.
Lee's treatment of abortion is misleading as well. For those who count the fetus as a person (and there are libertarians who do), abortion cries out not just for moral condemnation but for government intervention to protect the rights of the unborn.