Notes

André Cruz asked me why wasn't his ~/.bash_completion.d/ being used by default.

Well, its a feature of the bash_completion system that you must activate by hand. In my ~/.bashrc I have the following code:

bash=${BASH_VERSION%.*}; bmajor=${bash%.*}; bminor=${bash#*.}
if [ "$PS1" ] && [ $bmajor -eq 2 ] && [ $bminor '>' 04 ] ; then
  if [ -f ~/bin/bash_completion   ] ; then
    BASH_COMPLETION=~/bin/bash_completion
    BASH_COMPLETION_DIR=~/.bash_completion.d
    export BASH_COMPLETION BASH_COMPLETION_DIR
    . ~/bin/bash_completion
  fi
fi  
unset bash bmajor bminor

The trick is the BASH_COMPLETION_DIR setting before you source the bash_completion script. The BASH_COMPLETION environment is required because I keep a local copy of script.

I'm using the latest version of bash_completion, 20060301. If you download the 20060301 tarball, check the README file. There is a FAQ at the end that mentions this and other cool tricks.