I just finally got rid of my 1995 Ford F-150: I donated it to Cars 4 Causes. So far, the process has been simple. I called them up at 1-800-766-2273 and told them about the car (make, model, mileage, condition, etc.) and they evaluated whether or not they would accept it. After running it by the “acquisitions” folks, they said they’d take the thing.
They are making arrangements with my friend (whose driveway has been home to the car for the last 5 months) to pick it up at no cost to me. I’m mailing them the title, and when they receive the car they will mail me the paperwork with a bill of sale. Then I can finally take it off my insurance and stop paying property tax on it.
Separate from their web site, you can also find their blog, including FAQ and easy steps in a searchable, conversational format. Good stuff. This made it very user-friendly for me to take care of donating my car located in Connecticut while I am living in Chicago.
Choose your Charity
According to the Frequently Asked Questions, Cars 4 Causes allows car donors to choose the charity which receives 50% of the proceeds from the sale of their donated vehicle. I’m excited that I’ll be able to provide an extra little gift of at least a few hundred dollars to one of my favorite charities.
Other Resources
Check out the IRS guidance for car donors in Publication 4303 here.
Check out the charitable status of any organization through the online version of Publication 78, which is the updated list of nonprofits in good standing maintained by the IRS here
As an example, here are the search results (which are affirmative) for Cars 4 Causes as of January 13, 2009:

Cars 4 Causes on IRS Pub 78
Other Car Donation Services:
Put “Donate Car to Charity” in Google and you’ll pull up 342,000 results, there are lots of organizations with similar names and similar services. Some organizations are nonprofits themselves, such as Cars 4 Causes. Others are for-profit middlemen who handle all the details of the transaction (and I believe are paid a fee by the charities they support). Whether you work with a for-profit or nonprofit, some part of the proceeds from the sale of your car will have to pay the expenses to run the car donation operation, I don’t think it’s necessarily a bad thing to work with a for profit management company as long as they are not charging unreasonable fees to their charity partners (isn’t that what we like about social enterprises?). No matter who you work with, just be sure to check out any organization and make sure you understand how the process works, what portion of the sale price of the car goes to charity and what you will be able to deduct, and what you are responsible for.
Author’s note 3.20.09: Because of the increasingly hostile and unsupported comments from some spammers, I have closed comments on this post. Everyone’s gotten to say their peace, and I don’t feel additional debate is useful. Read through the comments and make your own decision about donating your car to the charity of your choice.