Hinduism is the oldest living religion in the world, existing since about 1500 BC in India. Worldwide, its practitioners are estimated at 750 million.
Hindus believe in a single god/collective soul named Brahman who is absent of qualities, divided into different aspects (lesser gods) with definite qualities. The most important gods are Brahma (the Creator), Vishnu (the Preserver), and Shiva (the Destroyer). Shakti, the wife of Shiva, is also important to many Hindus. She, like her husband, has many aspects. Durga and Kali are both beloved goddesses of motherhood, but Parvati and Uma are feared goddesses of destruction. This concept of differing-aspects-in-one is indicative of the way Hindus view their world -- they see it in constant change from creation to destruction, and from birth to death.
Hindus also view the world as degenerative. They believe that the world begins in a Golden Age and then gradually disintegrates, until Shiva finally destroys it in fire and flood. Brahma then recreates the world in another Golden Age.
Life is also seen as cyclical, and Hinduism teaches both reincarnation and karma. Hindus believe that the soul is eternal, so that when the body dies, the soul lives on and is given a new body. Karma, then, is the culmination of all the actions that a person took in his life, and affects which form his next life will take. If it was a good life, there was good karma and the soul will be reborn into a higher form (such as a higher caste1). But if it was a bad life, then the soul will be reborn into a lower form of life, such as a worm or insect. Thus Hindus believe that both animals and humans have souls; most abstain from meat (vegetarianism does depend on caste), and beef is forbidden to all.
Once the soul has reached spiritual perfection, it enters a new plane called moksha and joins with the universal Brahman. There are three ways that moksha can be achieved -- through works (good karma), realization (meditation on the godhead and illusory nature of everything that appears to be real), or through passionate devotion to God.
Hindus worship individually in temples which are devoted to one particular important god or goddess, but contain shrines for many other, smaller, gods. These shrines contain statues of the divinities, which are worshipped by entertaining them like human guests with food and gifts. Hindus believe that the divinity really inhabits these statues and thus they do not worship idols. Many people also have shrines at home, which they use to daily worship a particular god chosen by the family.
Saints in Hinduism are determined by importance and station of life. Both living and dead men can be worshipped as saints, and regions and localities choose which local men are worthy. Parents are sacred to their children, and teachers are sacred to their students.