Available variables

$breadcrumb
HTML for displaying the breadcrumbs at the top of the page.
$closure
Needs to be displayed at the bottom of the page, for any dynamic javascript that needs to be called once the page has already been displayed.
$content
The HTML content generated by Drupal to be displayed.
$directory
The directory the theme is located in , e.g.
themes/box_grey or themes/box_grey/box_cleanslate.
$footer_message
The footer message as defined in the admin settings.
$head
HTML as generated by drupal_get_html_head().
$head_title
The text to be displayed in the page title.
$help
Dynamic help text, mostly for admin pages.
$is_front
True if the front page is currently being displayed. Used to toggle the mission.
$language
The language the site is being displayed in.
$layout
This setting allows you to style different types of layout ('none', 'left', 'right' or 'both') differently, depending on how many sidebars are enabled.
$logo
The path to the logo image, as defined in theme configuration.
$messages
HTML for status and error messages, to be displayed at the top of the page.
$mission
The text of the site mission.
$node
(5.x and after only)If you are in page.tpl.php displaying a node in full page view then $node is available to your template.
$onload_attribute
(4.7 and older only) Onload tags to be added to the head tag, to allow for autoexecution of attached scripts.
$primary_links (array)
An array containing the links as they have been defined in the phptemplate specific configuration block.
$scripts
(5.x and after only) HTML to load the JavaScript files and make the JS settings available. Previously, javascript files are hardcoded into the page.tpl.php
$search_box
True(1) if the search box has been enabled.
$search_button_text
(4.7 and older only) Translated text on the search button.
$search_description
(4.7 and older only)Translated description for the search button.
$search_url
(4.7 and older only) URL the search form is submitted to.
$secondary_links (array)
An array containing the links as they have been defined in the phptemplate specific configuration block.
$sidebar_left
The HTML for the left sidebar.
$sidebar_right
The HTML for the right sidebar.
$site
The name of the site, always filled in.
$site_name
The site name of the site, to be used in the header, empty when display has been disabled.
$site_slogan
The slogan of the site, empty when display has been disabled.
$styles
Required for stylesheet switching to work. This prints out the style tags required.
$tabs
HTML for displaying tabs at the top of the page.
$title
Title, different from head_title, as this is just the node title most of the time.