FastX!

TightVNC is a free remote control software package. With TightVNC, you can see the desktop of a remote machine and control it with your local mouse and keyboard, just like you would do it sitting in the front of that computer. TightVNC is licensed under the GNU General Public License version 2.

AnyDesk is the world's most comfortable remote desktop application. Access all your programs, documents and files from anywhere, without having to entrust your data to a cloud service.

VNC is remote access and control software which allows you to view and fully interact with one computer desktop (the "VNC Connect") using a simple program (the "VNC viewer") on another computer desktop or mobile device anywhere on the Internet. The two computers don't even have to be the same type, so for example you can use VNC to view a Windows desktop at the office on a Linux or Mac computer at home.

NoMachine NX is an enterprise-class solution for secure remote access, desktop virtualization, and hosted desktop deployment built around the self-designed and self-developed NX suite of components. Thanks to its outstanding compression, session resilience and resource management and its integration with the powerful audio, printing and resource sharing capabilities of the Unix world, NX makes it possible to run any graphical application on any operating system across any network connection.NX is SSH encrypted, has random cookie generation, and is compressed for speed. Free version is available to everyone, and enterprise and server editions are available at cost. »

X2Go is an open source remote desktop software for Linux that uses the NX technology protocol. X2Go can be used to access PC desktops, but its main use case is providing secure standalone remote sessions via ssh. The server package must be installed on a Linux host; client packages can be run on Linux, OS X, or Windows.

Remote Access and Screen Sharing service. Free and Super Simple.

An open source remote desktop protocol (rdp) server

Window Switch is a tool which allows you to move applications between networked computers, the windows appear where you need them, as they were.You no longer need to save and send documents to move them around, simply move the view of the application to the machine where you need it.

DWService - Remote Access, Remote Support, Service Desk, offers a service that allows access to remote systems using a standard web browser.

ThinLinc - a remote desktop server from Cendio

Xpra is 'screen for X': it allows you to run X programs, usually on a remote host, direct their display to your local machine, and then to disconnect from these programs and reconnect from the same or another machine, without losing any state. It gives you remote access to individual applications.Xpra is "rootless" or "seamless": programs you run under it show up on your desktop as regular programs, managed by your regular window manager.Sessions can be accessed over SSH, or password protected over plain TCP sockets.Xpra is usable over reasonably slow links and does its best to adapt to changing network bandwidth limits. (see also adaptive JPEG mode)Xpra is open-source (GPLv2+), multi-platform and multi-language, with current clients written in Python and Java. »

(The InstaTech Client doesn't require you to set up a server. You can download and use it as is, which will utilize the instatech.org server. Setting up a server is only necessary for businesses wanting to use the live chat support feature.)