Tunnelblick is an open source GUI for OpenVPN on the Mac OS X platform. It gives you easy control over OpenVPN clients and server connections.
The app comes complete to use straight out of the box, with all the necessary binaries and drivers, including OpenVPN, easy-rsa, and tun/tap drivers. No additional installation files are required; all you have to do is simply add your configuration and encryption information.
In order to use Tunnelblick you will need access to a VPN server. Your Mac is one end of the tunnel and the VPN server is the other end.
Usefully, Tunnelblick supports the Apple Keychain in order to store your username and passwords, or your certificate passphrase, so you don't have to re-enter it again and again.
Overall, Tunnelblick is a great app that is user-friendly and unobtrusive. With it, you can take control over a OpenVPN client and server connections, all from within a simple and uncluttered interface.