You could also donate them to habitat for humanity or a similar orginization if in your area. School systems often have construction classes typically at high school or junior college levels where they might be able to use them.

Dont drop them in the landfill until you see if there is a hazmat dropoff in your area. Ours is at the county landfill and they accept them once a month. There might be other drop off points in your town or county.

also in our area Benjamin Moore will let you pay them to take them (samples and other paint). I know sounds awful to pay them yet again but it's pretty cheap. Much cheaper than trying to dry them out with cat litter IMO. It's like 75 cents for a quart and goes up per size of container. They have a printed brochure to help you with the details and prices for them to dispose of them for you. They do recycle the paint which was important to me.

Our recycling center takes them, but the curbside recyclers do not. If you're in a pinch, you might try calling recycling centers in your area or on a convenient route.