Howtoforge posted a guide about setting up an OpenVPN Server with authentication against OpenLDAP on Debian 6.0 (Squeeze)

OpenVPN, or Open Virtual Private Network, is a tool for creating networking "tunnels" between and among groups of computers that are not on the same local network. This is useful if you have services on a local network and need to access them remotely but don't want these services to be publicly accessible. By integrating with OpenSSL, OpenVPN can encrypt all VPN traffic to provide a secure connection between machines.

  Set Up OpenVPN Server With Authentication Against OpenLDAP On Debian 6.0 (Squeeze)