If your paint is still good and you just no longer need it, you may want to see if you have a local Habitat for Humanity. Habitat for Humanity accepts donations of new and used construction items and then uses them or sells them in their stores to get money to help more people. They may also mix the paint with others to make up a gallon of odd color paint that can be used for a primer coat or where color doesn't matter.
If the paint has hardened you'll need to find another way to get rid of the paint. Contact your local trash pickup. Many of them take paint for recycling right from the curb.
If you're local trash pickup service does not take paint, contact your local waste processing facility. Most dumps have extensive recycling facilities and often take things you never knew could be recycled. Ask for the Household Hazardous Waste facility. They should take old paint there. If not ask them to consider instituting a new recycling paint program. You may have to pay a hazardous waste fee when dropping off your paint, but it is much better than polluting by just throwing the paint away. Plus, many states have laws against improperly disposing of paint.
You can also search on the link in the resources section for a paint recycling place near you. Depending upon your area, there may be several nearby that you never knew about. More recycling facilities are developing all the time.