In my opinion its always best to use up the paint you have if you can. If you have no use for it donate it to a friend or list it on Freecycle or Craigslist to see if someone else could use it first before recycling.
There are ways to recycle paint. Paint is either oil based or a latex (water) based. Oil based paints can be recycled and should be taken to your local recycling facility that accepts household hazardous waste. In the Chicago area Goose Island in the city accepts oil based paint for recycling. In the suburbs the Naperville recycling center accepts oil based paint from any resident of Illinois.
Latex paints are not accepted at the recycling facilities but are accepted at some local hardware stores and other businesses. Latex paint can be dried out and put in with your everyday trash. Dry out the paint by leaving the lid off. This may take several weeks depending on how much paint is left in the can. Kitty litter can be added to quicken the process. Once dried the container can be placed in the trash. Personally I prefer not to throw it all in the trash so I remove the hardened paint from the can, recycle the paint can, and put the dried paint in the trash.
Check with your local recycling, trash, or city facility to see what is accepted in your city.