Panels is one of those Drupal modules that engenders a range of feelings around here. Some people love it -- interface configurable layout! -- and some hate it -- difficult to manage .5em gutters. But it, and Chaos Tools which it is based on, provide a great deal of useful functionality. The problem is there is very little documentation on how to extend it beyond what's distributed in code. The basics of extending Panels/CTools is pretty easy, you just implement the hook_ctools_plugin_directory to tell it where to look for your files, e.g.