• The Ṛigveda - hymns (mantras) that formulate the mythology of ancient Vedic practice
• The Sāmaveda - mantras from the Rig Veda, but arranged in an order specifically suited to the Soma sacrifice
• The Yajurveda - detailed prose instructions for the sacrifices
• The Atharvaveda - semi-magical spells against enemies, sorcerers, diseases and mistakes made during the sacrificial ritual, as well as kingly duties and some deeper spiritual truths.

They are available at Sacred Texts http://www.sacred-texts.com/hin/index.htm