Modify Global Mac OS X Path
If that's for a single user, you can add export PATH=/new/path:${PATH} to ~/.bash_profile. If it's going to be really global (for all users), then add it to /etc/profile and make sure the users have permission to access the path you're including. After that, you need to re-launch the shell, or reload the configurations with source /etc/profile or source ~/.bash_profile.