Charity shops (like Oxfam, but you can check the Golden Pages to see what's available in your area) would be delighted to get them; otherwise put an ad on Buy and Sell (it's free if you post it online and it's under a certain amount of words) and say they are free to take away - useful for rented accommodation, etc. Unless you want to do a car boot sale...
If the plates are chipped you could use them as saucers for plants; chipped mugs and cups can be used as small flowerpots (great for little bulbs like miniature narcissus, cyclamen or snowdrop).