State liability laws differ but in general as the car owner you have vicarious liability for those that operate the vehicle. Though you may not personally give permission to the person using the car if your son, who is in possession of the vehicle by your permission, gives the person permission to use the car they are an authorized driver usually in the eyes of an insurance company.

Insurance follows a car first and driver second normally so if your son's friend had an accident in the car than your insurance would be used as the primary and the driver's as secondary or excess. If you have are worried that your insurance limits would not be high enough to cover an accident, by your son that is in college or whoever he lets drive the car, than you may want to consider an Umbrella policy. An umbrella policy may help you be able to protect your personal assets better than just a car insurance policy on its own.

With an Umbrella policy you list what items you want covered (i.e. home, boat, cars, motorcycle, etc) and then those listed items are underwritten and a rate is given for the premium to cover up to $1 million in liability.

Even if the car is re-titled in your son's name you may want to check with a legal professional to make sure you would not be able to be held liable for your son's actions in his vehicle in any way. For example if he is still listed as a dependent on your taxes and lists your house as his permanent resident than you may be held liable for his actions still so again check with a lawyer in your state to see what your liability would be if you do change the car's title and insurance into your son's name only.

You and your son would also need to check and see if he would be able to register and insure the car in your state or if he would need to do so in the state in which he is attending college since that is where he is located the majority of the year. Your Department of Motor Vehicles should be able to answer the registration question while the insurance question can be answered by your insurance agent.