A really quick apache / php proxy script.

.htaccess

Options -Indexes

RewriteEngine on

# Add Slashes
RewriteCond %{REQUEST_URI} !(/$|\.) 
RewriteRule (.*) %{REQUEST_URI}/ [R=301,L]

# Force a domain - optional
# RewriteCond %{HTTP_HOST} .
# RewriteCond %{HTTP_HOST} !^example\.com [NC]
# RewriteRule (.*) http://example.com/$1 [R=301,L]


# Redirect to index.php
RewriteCond %{REQUEST_FILENAME} !-d
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule . index.php [L]

index.php

<?php
$ch = curl_init();
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
curl_setopt($ch, CURLOPT_VERBOSE, 1);
curl_setopt($ch, CURLOPT_HEADER, 1);
curl_setopt($ch, CURLOPT_URL, "http://this_will_show_up.com/subfolder/" . $_SERVER["REQUEST_URI"]); 
$response = curl_exec($ch); 
$header_size = curl_getinfo($ch, CURLINFO_HEADER_SIZE);
$header = substr($response, 0, $header_size);
$body = substr($response, $header_size);

foreach(explode("\n", $header) as $i){
	header($i); 
}

echo $body; 
?>