You can try mine:

external.samsill.com/translation

just be aware, it is still in a bit of a beta state, but it works.

One thing that will help if you do use it.  When you create the TranslationEngine, keep it if possible.   There is a bit of overhead when it gets the languages from the API.

Try this in a new Console Application. You'll need to add some references:

namespace LcApiExample

{

    using System;

    using System.Net.Http;

    using System.Net.Http.Headers;

    using System.Runtime.Serialization.Json;

    using System.Text;

    using System.Xml;

    using System.Xml.Linq;

    using System.Xml.XPath;

    class Program

    {

        static void Main(string[] args)

        {

            string apiKey = "[ENTER YOUR API KEY HERE]";

            string sourceText = "Hello Developers";

            string sourceLanguage = "eng";

            string targetLanguage = "fra";

            string json = string.Format(@"{{""text"":""{0}"",""from"":""{1}"",""to"":""{2}""}}", sourceText, sourceLanguage, targetLanguage);

            var client = new HttpClient();

            var requestMessage = new HttpRequestMessage(HttpMethod.Post, "https://lc-api.sdl.com/translate");

            requestMessage.Headers.Add("Accept", "application/json");

            requestMessage.Headers.Add("Authorization", string.Format("LC apiKey={0}", apiKey));

            requestMessage.Content = new ByteArrayContent(Encoding.UTF8.GetBytes(json));

            requestMessage.Content.Headers.ContentType = MediaTypeHeaderValue.Parse("application/json; charset=UTF-8");

            HttpResponseMessage response = client.SendAsync(requestMessage, HttpCompletionOption.ResponseContentRead).Result;

            if (response.IsSuccessStatusCode)

            {

                byte[] responseBytes = response.Content.ReadAsByteArrayAsync().Result;

                XmlReader reader = JsonReaderWriterFactory.CreateJsonReader(responseBytes, new XmlDictionaryReaderQuotas());

                XElement root = XElement.Load(reader);

                XElement translation = root.XPathSelectElement("//translation");

                Console.WriteLine(translation.Value);

            }

            else

            {

                Console.WriteLine("#ERROR: " + Encoding.UTF8.GetString(response.Content.ReadAsByteArrayAsync().Result));

            }

            Console.ReadKey();

        }

    }

}