To display your latest tweet on your site just add the following function in your functions.php file.

function stf_get_latest_tweet($username){

	$tweet = get_option("stf_lasttweet");
	
	$url = "http://search.twitter.com/search.atom?q=from:" . $username . "&rpp=1";
	
	if ($tweet['lastcheck'] < ( mktime() - 60 ) ) {

		$feed = file_get_contents( $url );
		$stepOne = explode("<content type="html">", $feed);
		$stepTwo = explode("</content>", $stepOne[1]);
		$output = $stepTwo[0];

		$output = htmlspecialchars_decode ( $output , ENT_QUOTES ); // Decode all HTML entities
		
		$tweet['lastcheck'] = mktime();
		$tweet['data'] = $output;
		
		update_option( 'stf_lasttweet', $tweet );
		
	} else {
	  $output = $tweet['data'];
	}

	return $output;
}

This function returns your latest tweet as html. To display it on your site use this call anywhere you like in your theme:

<?php echo stf_get_latest_tweet("shailancom"); ?>

Enjoy!