There's a reason people say, "You get what you pay for." Expecting something for nothing will generally leave you disappointed or deluded.
Free tarot sites (as well as other free divination services online) are generally automatic computer-generated spreads with fixed, pre-programmed meanings associated with each card. No human is involved in the process and, thus, there is no interpretation of the cards based on placement, combination with each other, or the specifics of your question.
For those serious about tarot reading, those contributions from a human reader are exactly what make tarot work. As such, computerized tarot readings should perhaps not be considered "readings" at all but instead simply a random dealing of cards.
On the other hand, if you are looking at tarot for purely entertainment purposes, then free online readings may suit your needs just fine. They can even be used by those learning how to read cards or who want to do a reading themselves but do not have their own card deck.
Www.facade.com/tarot has a fairly sophisticated computerized tarot system set up. You can choose from multiple deck designs (which might help you in eventually choosing a deck for purchase) as well as multiple spreads. The site then displays the dealt cards as well as giving textual explanations of each card.