How do I automatically load a bunch of JS/CSS from sites/all/libraries without hook_library?
Assuming you are on Drupal 7, drupal_add_library() will do just that for you. From the function's API page:


  Adds multiple JavaScript or CSS files at the same time.
  
  A library defines a set of JavaScript and/or CSS files, optionally
  using settings, and optionally requiring another library. For example,
  a library can be a jQuery plugin, a JavaScript framework, or a CSS
  framework. This function allows modules to load a library
  defined/shipped by itself or a depending module, without having to add
  all files of the library separately. Each library is only loaded once.


http://api.drupal.org/api/drupal/includes!common.inc/function/drupal_add_library/7

Note that you first need to define and register the library with hook_library().

http://api.drupal.org/api/drupal/modules%21system%21system.api.php/function/hook_library/7