Website to test POSTing a JSON file?

I'm learning how to use REST to GET and POST a JSON file from/to a server. I know there are several public APIs that let me test GETting a JSON file just to see if it's working, such as http://ift.tt/1guh8lS

But I would like to know if there's some API like those that would let me POST a JSON file to, then check if the server received it properly?