In an increasingly pluralistic society people of all faiths are neighbors. As a purely practical matter, since we're all going to work, study, and play together with people of different faith traditions, we'd better understand who it is we're relating to and what they believe. Buddhism, Hinduism and Islam, among others, are, like Christianity itself, an important part of the culture and history of the world. Your personal faith may actually grow wider and deeper as a result of encountering the religious other.
World religions are fascinating and fun to study.
Learning about them is part of the joy of discovering what it means to be human. They are often involved in situations of dire conflict that could affect your life in important ways, such as the price of heating oil or gas. It's impossible to understand events happening on a global scale without taking into account the role of various world religions. The Association for Religion and Intellectual Life has assembled a list of the most informative Internet resources concerning world religions, including Christianity.