On Google Spreadsheet form submission, push new entry to a MailChimp subscription list with an `onformsubmit` trigger. Uses the MailChimp API and Google Apps Script.

gistfile1.js

var API_KEY = 'xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx';
var mc_base_url = 'http://us7.api.mailchimp.com/1.3/?method=listSubscribe';
var mc_list_id = 'xxxxxxxxxx';
var mc_double_optin = false;


/**
 * Uses the MailChimp API to add a subscriber to a list.
 */
function sendToMailChimp_(fn, ln, em, yr){
  var payload = {
    "method": "listSubscribe",
    "apikey": API_KEY,
    "id": mc_list_id,
    "merge_vars[FNAME]":fn,
    "merge_vars[LNAME]":ln,
    "merge_vars[YEAR]":yr,
    "email_address": em,
    "double_optin": mc_double_optin,
    "update_existing": false
  };
  var options = {
    "method": "post",
    "payload": payload
  };
  
  var response = UrlFetchApp.fetch(mc_base_url,options);
  Logger.log(response)
}

/**
 * Trigger function. Based on Google Script tutorial.
 * @param {Object} e The event parameter for form submission to a spreadsheet;
 *     see https://developers.google.com/apps-script/understanding_events
 */
function onFormSubmit(e) {
  
  var fname = e.namedValues['Name'][0].split(" ")[0];
  var lname = e.namedValues['Name'][0].split(" ")[1];
  var email = e.namedValues['Email'][0];
  var year = e.namedValues['Stuyvesant Graduation Year'][0];
  
  sendToMailChimp_(fname,lname,email,year);
  
}

/**
 * Main function. Creates onFormSubmit trigger.
 */
function myFunction(){
  // Was separated line by line for debugging purposes.
  var sheet = SpreadsheetApp.getActive();
  var a = ScriptApp.newTrigger("onFormSubmit");
  var b = a.forSpreadsheet(sheet);
  var c = b.onFormSubmit();
  var d = c.create();
}