Requires:
PHP
GD
Write access to site folder from PHP

Setup:
1) Put this all in the root of your site

2) create an empty thumbs/ folder in your site root

3) create an empty images/ folder in your site root

4) Drop images into the images/ folder. create folders under this folder with images. go nuts.

5) 'chmod -R 777 *' in the root of your new gallery site

6) Load up the site. Ta-da - a quick, simple gallery with lightbox and left/right controls.

Notes:
Thumbs are created as-needed, and only once. So you can add images to the images/ folder and new thumbs will be created
on the fly on next load of the page - per folder.

When removing images thumbs are not removed automatically. So, to save disk space, make sure to remove the
thumbs from the thumbs/ folder

The upload/ folder allows you to upload new files via the web without using FTP. Password-protect this folder, or rename it, for enhanced security so someone isn't uploading into your gallery. It currently uploads into the images root and does not access folders.

Shoutouts:
Shoutouts to all the open source projects used here: PHP, jQuery, fancybox