Here's the code for my Arduino MEGA2560 and whatever Ethernet shield I got.

It came from sparkfun's example page and I just added reading the six analog inputs, averaging several samples and converting to degree-F before pushing the data to sparkfun.

/*****************************************************************
Phant_Ethernet.ino
Post data to SparkFun's data stream server system (phant) using
an Arduino and an Ethernet Shield.
Jim Lindblom @ SparkFun Electronics
Original Creation Date: July 3, 2014

This sketch uses an Arduino Uno to POST sensor readings to 
SparkFun's data logging streams (http://data.sparkfun.com). A post
will be initiated whenever pin 3 is connected to ground.

Before uploading this sketch, there are a number of global vars
that need adjusting:
1. Ethernet Stuff: Fill in your desired MAC and a static IP, even
   if you're planning on having DCHP fill your IP in for you.
   The static IP is only used as a fallback, if DHCP doesn't work.
2. Phant Stuff: Fill in your data stream's public, private, and 
data keys before uploading!

Development environment specifics:
    IDE: Arduino 1.0.5
    Hardware Platform: RedBoard & PoEthernet Shield

This code is beerware; if you see me (or any other SparkFun 
employee) at the local, and you've found our code helpful, please 
buy us a round!

Much of this code is largely based on David Mellis' WebClient
example in the Ethernet library.

Distributed as-is; no warranty is given.
*****************************************************************/
#include <SPI.h> // Required to use Ethernet
#include <EthernetV2_0.h> // The Ethernet library includes the client

///////////////////////
// Ethernet Settings //
///////////////////////
// Enter a MAC address for your controller below.
byte mac[] = { 0xDE, 0xAD, 0xBE, 0xEF, 0xFE, 0xED };
// if you don't want to use DNS (and reduce your sketch size)
// use the numeric IP instead of the name for the server:
//IPAddress server(54,86,132,254);  // numeric IP for data.sparkfun.com
char server[] = "data.sparkfun.com";    // name address for data.sparkFun (using DNS)
// Set the static IP address to use if the DHCP fails to assign
IPAddress ip(192,168,2,200);

// Initialize the Ethernet client library
// with the IP address and port of the server 
// that you want to connect to (port 80 is default for HTTP):
EthernetClient client;

/////////////////
// Phant Stuff //
/////////////////
const String publicKey = "YOURPUBLIKKEY";
const String privateKey = "YOURPRIVATEKEY";
const byte NUM_FIELDS = 6;
const String fieldNames[NUM_FIELDS] = {"boilerout", "boilerreturn", "zone2out", "zone2return", "zone3out", "zone3return"};
String fieldData[NUM_FIELDS];
#define BOILEROUT     0
#define BOILERRETURN  1
#define ZONE2OUT      2
#define ZONE2RETURN   3
#define ZONE3OUT      4
#define ZONE3RETURN   5

#define LEDPIN 13
//////////////////////
// Input Pins, Misc //
//////////////////////
#define SDCARD_CS 4

bool print = 0;

void setup()
{
  // Set Up Ethernet:
  // start serial port:
  Serial.begin(9600);
  pinMode(SDCARD_CS,OUTPUT);
  pinMode(0, INPUT);
  pinMode(1, INPUT);
  pinMode(2, INPUT);
  pinMode(3, INPUT);
  pinMode(4, INPUT);
  pinMode(5, INPUT);
  
  pinMode(LEDPIN, OUTPUT);
  
  digitalWrite(SDCARD_CS,HIGH);//Deselect the SD card
  
  // give the ethernet module time to boot up:
  delay(1000);
  // start the Ethernet connection:
  if (Ethernet.begin(mac) == 0) {
    if(print) Serial.println("Failed to configure Ethernet using DHCP");
  }

  Serial.println(F("=========== Ready to Stream ==========="));
}

void loop()
{
  int i,j;
  float temps[NUM_FIELDS][10];
  float average[NUM_FIELDS];
  char buffer[80];  // Buffer to convert from binary to ASCII

  // Read each sensor ten times at a rate of 1 Hz. THis takes (10 times NUM_SAFIELDS) in seconds (60 for this example)
  for(i=0;i<10;i++) {
    for(j=8;j<8+NUM_FIELDS;j++) {
      analogRead(j);
      delay(10);
      analogRead(j);
      delay(10);
      temps[j-8][i] = ((((analogRead(j) * 5.0) / 1024.0) - 0.5) * 100 * 9.0 / 5.0) + 32.0;
      if(print) Serial.print(j-8); if(print) Serial.print(" ");if(print) Serial.println(temps[j-8][i]);
      delay(166);
    }
  }
  
  // Calculate the sum of the last ten samples
  for(j=0;j<NUM_FIELDS;j++) {
      average[j] = 0.0;
  }
  for(i=0;i<10;i++) {
    for(j=0;j<NUM_FIELDS;j++) {
      average[j] += temps[j][i];
    }
  }
  
  // Calculate the average of the samples and fill in the output fieldData array
  for(j=0;j<NUM_FIELDS;j++) {
    fieldData[j] = dtostrf(average[j] / 10.0, 3, 1, buffer);
    if(print) Serial.print(fieldData[j]); if(print) Serial.print(" ");
  }
  if(print) Serial.println();
  
  digitalWrite(LEDPIN, HIGH);
  if(print) Serial.println("Posting!");
  postData(); // the postData() function does all the work
  digitalWrite(LEDPIN, LOW);
  }

void postData()
{
  // Make a TCP connection to remote host
  if (client.connect(server, 80))
  {
    // Post the data! Request should look a little something like:
    // GET /input/publicKey?private_key=privateKey&light=1024&switch=0&name=Jim HTTP/1.1\n
    // Host: data.sparkfun.com\n
    // Connection: close\n
    // \n
    client.print("GET /input/");
    client.print(publicKey);
    client.print("?private_key=");
    client.print(privateKey);
    for (int i=0; i<NUM_FIELDS; i++)
    {
      client.print("&");
      client.print(fieldNames[i]);
      client.print("=");
      client.print(fieldData[i]);
    }
    client.println(" HTTP/1.1");
    client.print("Host: ");
    client.println(server);
    client.println("Connection: close");
    client.println();
  }
  else
  {
    if(print) Serial.println(F("Connection failed"));
  } 

  // Check for a response from the server, and route it
  // out the serial port.
  while (client.connected())
  {
    if ( client.available() )
    {
      char c = client.read();
      if(1) Serial.print(c);
    }      
  }
  if(1) Serial.println();
  client.stop();
}

void setupEthernet()
{
  if(print) Serial.println("Setting up Ethernet...");
  // start the Ethernet connection:
  if (Ethernet.begin(mac) == 0) {
    if(print) Serial.println(F("Failed to configure Ethernet using DHCP"));
    // no point in carrying on, so do nothing forevermore:
    // try to congifure using IP address instead of DHCP:
    Ethernet.begin(mac, ip);
  }
  if(print) Serial.print("My IP address: ");
  if(print) Serial.println(Ethernet.localIP());
  // give the Ethernet shield a second to initialize:
  delay(1000);
}