Drupal 7 comes with an Overlay module. Once you enable it, all admin links open in an overlay. But non-admin links do not open in the overlay by default. There is a way to open a non-admin link in the overlay. Use hook_admin_paths_alter().
/**
* Implements hook_admin_paths_alter().
*/
function mymodule_admin_paths_alter(&$paths) {
$paths['node/*'] = TRUE;
}
Now when you click on any node link, it will open in an overlay. Wasn't that simple?
