IRS Warns of Sham Charities Looking for Used Cars
Before donating a vehicle to charity, the IRS suggests you make sure the charity is a bona fide tax exempt organization, which you can do easily by examining IRS Publication 78, Cumulative List of Organizations. The publication is available for downloading  from the IRS Web site, or you can perform a search  for an organization without having to download the entire publication.
When valuing the donated vehicle for purposes of taking a tax deduction, you should compute the "fair market value" of the vehicle, taking into consideration the current Blue Book  value, and factoring in the age and condition of the vehicle and the miles that it has been driven.
Be sure to check your state law to verify the rules for handling a transfer of title.