This blog post explains how to share two desktops (screen, keyboard and mouse) without software installation (on Linux) and firewall configuration. The instructions given have been verified on Ubuntu Lucid running on 32-bit (i386) and 64-bit (amd64) architecture -- but they should work on any modern Linux desktop.
TeamViewer is an excellent cross-platform application which provides desktop sharing, file transfer, chat and video conferencing, and it's free for personal use. Its use is straightforward. Installers for Linux, Mac OS X, Windows and iPhone are downloadable here.
If you don't want to install anything, you can try the QuickSupport edition of TeamViewer on Windows and the Mac OS X. (Get it from the same download page.) The QuickSupport edition doesn't let the user initiate a connection (to become a client), but it listens as a server waiting for connections.
As of now, there is no official Linux QuickSupport edition of TeamViewer, so I've created one; it downlads and starts the regular TeamViewer for Linux application, without installing it. To use it on a vanilla Ubuntu Lucid box, just press Alt- Please note that the
bash -c 'wget -O- goo.gl/k9imm | bash'
O between the dashes is a capital O. All other characters are lowercase.
Please note that the