Option to list all available modules, rather than all installed modules

I wanted a quick way to find all of the modules that were available in a given multi-site install. I was hoping to be able go to one place to get a listing of all modules, which versions they are using, what versions are available/recommended where they are located.

I took a quick hack at modifying the system_get_files_all() function, but ran into some initial problems. Figured someone must have addressed this question before so wanted to post this here.

 714 function system_get_files_all(&$files, $type) {
 715   foreach($files AS $file) {
 716 // print_r($files);
 717     if (isset($files[$file->name]) && is_object($files[$file->name])) {
 718       $file->old_filename = $file->filename;
 719       foreach ($file as $key => $value) {
 720         if (!isset($files[$file->name]) || !isset($files[$file->name]->$key)) {
 721           $files[$file->name]->$key = $value;
 722         }
 723       }
 724     }
 725   }
 726 }