What's difference?

- http://drupal.org/project/drupalforfirebug
Drupal for Firebug is both a Drupal module and a Firefox Extension that extends the Firebug Firefox Extension to provide Drupal specific debugging and status messages. It allows users to see the processing of the node, form, views, and user objects and works with the Devel module to display SQL queries and execute PHP from the Firebug window.
You must download the DrupalForFirebug Drupal module [http://drupal.org/project/drupalforfirebug] and Firefox Extension [https://addons.mozilla.org/en-US/firefox/addon/8370].
Via: [http://drupalforfirebug.chapterthree.com/about]

- http://drupal.org/project/firebug ( by Steve McKenzie )
Steve McKenzie says: 'recode the firebug.js into jquery code'
Via: http://drupal.org/node/117116
develCuy says: 'Is a jQuery reimplementation of firebug_lite'
Via: http://drupal.org/node/433444

- http://drupal.org/project/firebug_lite ( by develCuy [http://drupal.org/user/125473] )
develCuy says: 'The purpose of my implementation is to get Firebug Lite working "as is", with just minor and unnoticeable changes.'
Via: http://drupal.org/node/433444

It seems like a mess.
1. Drupalforfirebug is a plugin wich lets Firebug to let Drupal have a debug console.
2. firebug.module and firebug_lite.module are 2 different implementations for the same approach. This situation is currently being solved at #446810: Merge with Firebug Lite module

Does it answer your question?