The conventional way of adding a new region to your theme in Drupal 7 is by editing the .info file and declaring it in there. However, there are ways you can achieve similar effects dynamically - from a custom module.

As you know, declaring a region in the theme’s .info file is not always useful: you have to manually declare it and it's not a useful way if you are writing a module that needs to dynamically create new regions. Enter hook_system_info_alter().

This Drupal hook takes three arguments(&$info, $file, $type) and alters the data transmitted to Drupal from both theme and module .info files. So in order to make Drupal register another region from your .module file, you would write something like this:

/*
 * Implements hook_system_info_alter().
 */
function your_module_name_system_info_alter(&$info, $file, $type) {
  if ($type == 'theme') {
    $info['regions']['region_machine_name'] = t('Region name');
  }
}

You need to make the following word replacements though:

• your_module_name = The machine readable name of your module;
• region_machine_name = The machine name of your region

This function will check that the type it targets to alter is a theme (not a module) and alters the $info variable by adding a new region - with its readable and machine names. But remember, for this to take effect, the caches need to be cleared. So if you intend to use this dynamically, don’t forget the existence of this functions: cache_clear_all();

OK, so hope this helps. Let me know if you run into some problems.