I have another How To Joomla article up: How to debug our Joomla code with FirePHP. Just recently, I discovered a plugin that painlessly adds FirePHP to your Joomla site. After installing it and doing some tests, I decided to write an article. In the midst of writing the article, I went to the FirePHP wiki and found another FirePHP plugin for Joomla released by the Kunena team. This one is even better, with tighter integration into the Joomla environment. I see many possibilities for model debugging and exception handling down the road.
Drupal and WordPress also have FirePHP plugins, as do most of the major stand-alone PHP frameworks. Have a look to see if your favorite is listed before trying to hack FirePHP into your next project.