VPN or Virtual Private Network allow tunnelling to create private networks with many types of encryption depending on the solution you choose. SSL, IPSEC, L2TP?, PPTP are some of the most popular encryption standards used for VPNs?.
http://www.answers.com/vpn
http://www.tinc-vpn.org/
http://www.vpnc.org/
http://vpn.shmoo.com/
http://www.vpn-software.info/
http://www.vpnlabs.org/