Rosamundwo.com

<div id="twitter">
<?php

// the function
/**
 * @desc Get latest tweet from a Twitter account
 * @param string The account's username
 * @return string The tweet
 */
function get_latest_tweet($username)
{
    $url = "http://search.twitter.com/search.atom?q=from:$username&rpp=1";
    $content = file_get_contents($url);
    $content = explode('<content type="html">', $content);
    $content = explode('</content>', $content[1]);
    return html_entity_decode($content[0]);
}

// now use it
$my_username = 'rosamundwo';
echo get_latest_tweet($my_username);
?>
<a href="http://twitter.com/rosamundwo"><br> <a href="http://www.twitter.com/rosamundwo/">Follow Me</a>
</div>

Demo