You may have heard otherwise, but Tarot cards did not enter the occult world until the very late 18th century, when Antoine Court de Gébelin published two essays on them in his massive 9-volume work Le monde primitif. Court de Gébelin ascribed their invention to ancient Egypt, but then he ascribed the invention of everything he liked to ancient Egypt, so you can't take that too seriously.
Now the first of these essays, by Court de Gébelin, analyzes the allegorical images of the Trumps. You have to remember that the game of Tarot, a Bridge-like game, had become very fashionable in Paris in that period. His analyses don't bear all that much relation to what have become the "standard" occult meanings, but they are interesting nonetheless.
The second essay, by his friend the Comte de Mellet, suggests that the cards are used for cartomancy, and although his proposed method (rather like the card-game War) isn't much like later spread divination, it's really here that the whole divination thing begins.
You can't as yet get the essays in English; I'm working on a translation.
Development
In the mid-19th century, Eliphas Lévi comes up with this nifty idea that since there are 22 Trumps, those should be connected to the 22 Hebrew letters, and he spins a whole occult theory out of this. His ideas are picked up by Papus and many others (Oswald Wirth leaps to mind immediately), and from this we get Tarot in the 19th century and 20th century.
Cards
If you're looking for "original" cards, you want a 19th century or earlier deck, such as one of the many that U.S. Games Systems prints. You will note immediately that only the Trumps have much imagery. The ascription of clear meanings to the "minor arcana," and indeed the notion of minor arcana itself, is relatively late.
References
Stuart Kaplan's Encyclopedia of Tarot (U.S. Games Systems) is good for images and some history.
Ronald Decker, Michael Dummett, and Thierry Depaulis's A Wicked Pack of Cards does a solid job of tracing the history of the cards in the occult, though they are much too positivistic and spend far too much time debunking.
Dummett has written a number of books on historical cards, but remember that his interest is really in reconstructing the history of the cards and the games played with them, and he thinks that all occult uses are stupid.
-- ChrisLehrich? - 17 Jan 2005