Texts Important to Hinduism: Please note that sources are mentioned as endnotes.

The fundamental canonical religious influence for most Hindus are the Vedas. The oldest(there are four)is the Rig Veda, which was written in a form of Sanskrit in northwest India.

The Rig Veda, probably created between the 13th and 10th Centuries BC and formed of nearly one-thousand-twenty-eight(1028) hymns to the gods of the Hindu pantheon, has often been memorized with ritualistic fervour, and to syllabic accuracy, while also preserved in Hindu orality to the present day. The Rig-Veda is supported by two other Vedas, the Yajur-Veda (the guidebook for sacrifice and such rituals) and the Sama-Veda (the hymnal).

The Atharva-Veda (a collection of spells), was probably added about 900 BC.

At this time,the Brahmanas - epic, and comprehensive Sanskrit texts explaining priestly ritual and the myths that created it-were written. At around 600BC, the Upanishads started being composed; these represent mysticaland philosophical meditations on the meaning of an almost Sartrianexistence and on the being and character of the universe.

The Vedas are regarded as divine canon(shruti, or, in Sanskrit, "what has been heard", likening them to the early Hebrew Scriptures),and changing it is fiercely prohibited. The true content of this canon, is, unfortunately, unknown to most Hindus.

Another pragmatic compendium is contained in the "Smriti", or "what is remembered," which is also orally continued, and is not completely unlike the Hebrew scripture Leviticus, and the parables of Jesus Christ combined. However, no prohibition is made against improvising, creating variations on the themes of, rewording, or even challenging the Smriti, which reflects its roots in the Hindu people, not in their divinities.

The Smriti includes the two weighty Sanskrit epics,the 'Mahabharata' and the 'Ramayana", as well as the many Sanskrit Puranas, which include 18 'Great' Puranas and dozens morelesser Puranas as well as many Dharmashastras and Dharmasutras (teachings on sacred law).

The two epics are built around epic narratives. The Mahabharata retells of the war between the Pandava brothers, led by their cousin Krishna, and their cousins, the Kauravas, setting up for the later work, the Bhagavad-Gita, in which Krishna plays raconteur to the young hero Arjuna.

The Ramayana tells of the journey of Rama to rescue his wife Sita after she is stolen by the demon Ravana, as well as well-crafted allegories designed to teach Hindus about the meaning of true marriage as seen by the gods. Rama and Sita are avatars of Vishnu and his mistress Lakshmi, and are sent to earth in order to set examples of idealised humanity. But these stories are embedded in a rich body of other tales and discourses on philosophy, law, geography, political science, and astronomy as well, so that in the end, the Mahabharata (around 200,000 lines long) becomes a kind of encyclopedia and literature, and the Ramayana (more than 50,000 lines long) is certainly in that range, especially once the era of Valmiki's life is taken into account.

However, because of the amount of information extrinsic to the story itself, it's impossible to trace their exact dates of creation, so we can only estimate that the main bodies of the Mahabharata and the Ramayana were probably written sometime between 300 BC and AD 300. Both, however, continued to grow even after they were translated into the vernacular languages of India (such as Tamil and Hindi) in the succeeding centuries. This was largely due to the popularity of the epics, and their entirely oral retelling, which made them open to much local reinterpretation.

The Puranas were written after the epic workss, and several of them develop themes found in the epics (for instance, the Bhagavata-Purana describes the childhood of Krishna, a topic not elaborated in the Mahabharata).

The Puranas also include auxiliary myths, hymns of praise to the gods, popular philosophies, iconography, and rituals.

Also, most of the Puranas are keyed towards different Hindu sects: the 'great' Puranas (and some smaller Puranas) are dedicated to the worship of Shiva or Vishnu, while several smaller Puranas are devoted to the popular, but minor deities,like Ganesha, Skanda and the sun.

In addition, they all contain a great deal of universally Hindu material, probably of earlier origin(before the creation of specific sects), such as the "five topics" (panchalakshana), of the Puranas: (1)the creation of the Universe, (2)the destruction and recreation of the Universe, (3)the dynasties of the solar and lunar Gods, (4)the genealogy in the pantheon and writers/sages, and (5)the ages of the ancestors of humankind.

Sources: Encarta Encyclopedia 97 edition(I think) India Mystica CD-ROM Britanica.com and a small bit of my IMHO commentary.