I bought a used car, but the dealer is not giving me the title.

The car is paid in full? Not financed? If financed, the leinholder will hold the title until all the obligations are met. If paid in full, you should have been handed the title during the signing.
I don't recommend even taking delivery of a vehicle unless the title is clear.
That same dealer isn't allowed to take in a vehicle without a clear title, in most states, unless it is a consignment sale.
Someone has that title and if it wasn't in your agreement to pay for it, the dealer needs to come up with it.
You need to get a lawyer involved in this matter.

Yes, in fact the dealer sold you a car he did not legally own, This is illegal in many states, the dealer is to have the title on site and merely sign it over when you pay in full, or send it to the lien holder and so on.

So this dealer is doing somehting illegal, it sounds like they bought this at auction and they were waiting for the title to come in, they are responsible for supplying a clear title, So if you signed the paper work and a full price decided, you don't owe any more money.

The dealer needs to pay this and provide you a title or give you all your money back.

If he does not supply a clear title very soon, yes you need an attorney.

You cannot legally title or register your vechile, get a tag and so on.
Without this paper work.

I would not hire an attorney yet. Try this.... You don't say what state you are located in... Most states require that auto dealers have a license to sell vehicles.... And in conjunction with that license, most states require a "surety bond" and that surety bond is conditioned upon the dealer faithfully handling transactions involvoing the selling of automobiles... If he promised you a valid title and has not furnished it ... Then that seems to be a possible violation of his dealer license.... Write the dealer a letter... Perhaps send it certified... Return receipt requested (keep a copy a the signed receipt when you get it back from the post office.... In that letter advise the dealer that you expect valid title to be furnished you within xxx number of days and in no event later than xx/xx/2008..... And if not received by that date, you will then file a claim on his surety bond....check with licensing authorities in your state to see if he did in fact post a surety bond as a condition of him obtaining a license.... Then when the deadline passes, simply send a letter to his surety company filing a claim for the value of the vehicle... Without this bond (and it will be in jeopardy until your issue is settled), the dealer cannot sell cars and he is out of business. I am not an attorney and this my advice is not and should not be considered legal advise.... It's simply a possible remedy you might want to pursue.

Ask you state attorney general to get involved...that will wake him up