The best known Tarot deck is the Rider-Waite-Smith deck. There are hundreds of others, but the images of the RWS Tarot are the ones which are instantly recognizable. This page has abundant detail about the history and significance of the RWS deck, as well as other texts about Tarot divination.
The Pictorial Key to the Tarot by A.E. Waite 
The Tarot of the Bohemians by Papus; tr. A. P
The Symbolism of the Tarot by P. D. Ouspensky
Rider-Waite-Smith Tarot Deck Copyright FAQ
Tarot Card Cross-reference. This is an index of all of the Tarot Card images at sacred-texts. Currently this includes the color 1909 RWS deck, the greyscale RWS images from the Pictorial Key, and the Wirth and Marseilles images from Tarot of the Bohemians.
Tarot Card Comparison, by J.B. Hare
NOTE ON THE COLOR TAROT CARD IMAGES: Holly Voley has scanned a set of vintage Tarot cards. These images can be viewed when you click on any of the black and white thumbnails in the Pictorial Key to the Tarot, or in the right-hand frame in the Tarot card reader. They can also be viewed sequentially in the Tarot Card Cross-reference.