My main productivity tool is emacs. I spend a lot of time configuring it to do my bidding. I use it as a news reader, mail client, chat interface, Japanese learning tool, web browser, organizer, calendar, etc... I even sometime use it for writing programs.
In 2007, I have declared .emacs bankruptcy like Ryan McGeary. My configuration file grew so large it was unmaintainable. I took the time to split it up in small manageable chunks.
The result was well worth the time invested. I have packaged all external programs that are not included in emacs 23.1: auctex, bbdb, lookup, org, w3m...
The start up files are in emacs.d. I have split files amongst different functionality groups. I compile all elisp files myself. A warning message will help me find my mistakes.