From: https://www.splashtop.com/

One user 10 computers

From: http://www.aeroadmin.com/en/

AeroAdmin - FREE and EASY remote desktop software! Set up remote desktop connection within a few seconds!

No installation, no configuration, works behind NAT.

Free of charge for business and home!
Works without installation
Quick start

From: https://www.join.me/

have remote person start a meeting

quickly share desktop

From: https://showmypc.com/

ShowMyPC is a company with a mission to provide free and integrated collaboration tools for 
all users. ShowMyPC relies on many open technologies and provides its services free to everyone. 
In addition, ShowMyPC offers Premium services and many integration options to continue growth,
research and development.

From: http://mediarealm.com.au/articles/2013/03/remotely-enable-remote-desktop-in-windows-7/

Step 3: Change a registry setting to enable Remote Desktop
It’s time to make use of the Remote Registry and actually enable RDP. Load up regedit and 
go to File > Connect Network Registry. Enter the name of your remote computer and connect 
to it. Navigate to HKEY_LOCAL_MACHINE > System > CurrentControlSet > Control > Terminal Server. 
Change the value of “fDenyTSConnections” to “0”.