TightVNC is a cross-platform free and open-source remote desktop software application.

Tinc VPN is a Virtual Private Network (VPN) daemon that uses tunneling and encryption to create a secure private network between hosts.

Haguichi is free and open source software.

LogMeIn Hamachi is a hosted VPN service that securely connects devices and networks, extending LAN-like network connectivity to mobile.

ZeroTier delivers VPN, SDN, and SD-WAN capabilities with a single system.