Presently you can learn everything about Tarot online.  For a great introductory guide to reading the Tarot, take a look at Joan Bunning's Learning the Tarot -- An On-Line Course. Ms. Bunning provides step-by-step lessons and exercises for learning to read the cards. The course is free, comprehensive and well-written.  Tarot Basics gives a good overview of the cards' relationships to one another.  For other advice, including information on alternative Tarot decks, try Voodoo Tarot

If you don't feel like dealing with the cards yourself, there are a number of sites that offer free online tarot card readings. Without question, the best is Tarot.   It features readings from seven different decks of cards, in a variety of formations from the simplest one-card reading to the venerable Cross and Triangle sperad. Tarot at Matrix is another well-designed free online Tarot reading.

You also can browse through the excellent collection of Tarot-related links at Links to the Tarot and Tarot Weekly