Baggage storage is now available in Terminal 8 as well. It's a third-party operation located near the domestic baggage claim area.

I recommend not leaving the airport property. You could always take the AirTrain over to Terminal 4 to check out the restaurants and shops there (large shopping area outside security). If you're really feeling adventurous, you could take the AirTrain to Jamaica ($5 each way) and wander the streets looking for a slice of pizza.