This is for my reference, in no particular order.. As vnc is not secure by default.. I will keep editing this as needed.. Open source/FLOSS applications are preferred.

##Winswitch (Based on xpra)
https://winswitch.org/

##x2go (Based on FreeNX)
http://wiki.x2go.org/doku.php/start

##Securing a VNC Server on Linux with SSH
http://www.serverwatch.com/server-tutorials/securing-a-vnc-server-on-linux-with-ssh.html

##QVD
http://theqvd.com/

##Uleto
https://en.wikipedia.org/wiki/Ulteo

##and the venerable wikipedia page-
https://en.wikipedia.org/wiki/Comparison_of_remote_desktop_software