Diggit Drupalextras

To those wishing to install Drush on their Mac, but having difficulty, here's a surefire way to get it running great:

1. Fire up the Terminal (this is why you're using Drush, so you'd better get comfy in here!).
2. cd to your Desktop, download drush, and extract it.
   
   $ cd Desktop
   $ wget http://ftp.drupal.org/files/projects/drush-6.x-3.3.tar.gz
   $ tar -xvzf drush-6.x-3.3.tar.gz
3. Move the drush directory to /usr/local/lib
   
   $ sudo mv drush /usr/local/lib
4. Make drush executable.
   
   $ sudo chmod u+x /usr/local/lib/drush/drush
5. Make a symbolic link to drush in /usr/bin
   
   $ sudo ln -s /usr/local/lib/drush/drush /usr/bin/drush
6. Set up an alias in your bash environment so you can type 'drush command' rather than '/usr/bin/drush command'
   
   $ cd ~
   $ nano .profile
   # Inside the .profile file:
   alias drush="/usr/bin/drush"
   # Then press control-O + return to write the file, and control-X to exit nano
   $ source .profile

Now, you can simply enter 'drush command' to use drush.