Uses the built-in dictionary in a *nix system to run through every word in the dictionary from shortest to longest and find available Twitter usernames. Usage: `php -f path/to/twitter.php`.

twitter.php

<?php
// Made by Ross Penman (@PenmanRoss, rosspenman.com)

ob_implicit_flush();


$words = trim(file_get_contents("/usr/share/dict/words"));
$words = explode("\n", $words);

$sorted_words = array();

foreach ($words as $word) {
  $len = strlen($word);
  if (!$sorted_words[$len]) $sorted_words[$len] = array();
  array_push($sorted_words[$len], $word);
}

// You can't have a Twitter username over 15 characters.
while (count($sorted_words) > 15) {
  array_pop($sorted_words);
}

// Twitter won't let new users register usernames less than three characters.
array_shift($sorted_words);
array_shift($sorted_words);

$flattened_words = array();

foreach ($sorted_words as $length) {
  foreach ($length as $word) {
    array_push($flattened_words, $word);
  }
}

$words = $flattened_words;

$available = array();

foreach ($words as $word) {
  echo "Trying $word\n";
  $response = json_decode(file_get_contents("https://twitter.com/users/username_available?context=signup&custom=true&email=&full_name=&suggest=1&suggest_on_username=true&username=$word"));
  if ($response->valid) {
    echo "Available";
    array_push($available, $word);
  } else {
    echo "Not Avilable";	
  }
  echo "\n\n";
}

echo "===================\nAviailable Usernames\n\n";

foreach ($available as $word) {
  echo "$word\n";
}

echo "===================\n\n";

Regarding https://twitter.com/PenmanRoss/status/313761056918999040 ... you could add this at the top:

// Discover unused twitter handles which are dictionary words between 3-15 characters in length.
//
// Copyright (C) 2013 Ross Penman http://rosspenman.com/ross
//
// Copying and distribution of this file, with or without modification,
// are permitted in any medium without royalty provided the copyright
// notice and this notice are preserved. This file is offered as-is,
// without any warranty.