Top two recommend free remote desktop sharing tools

ShowMyPC

Show computer - http://download3.showmypc.com/ShowMyPC3005.exe
View computer - http://download3.showmypc.com/ShowMyPC3005.exe

Allows online collaboration, desktop sharing, and remote PC access. No registration required, no login and easy to use. Uses SSH to make remote connections.

Zolved  

Show computer - http://www.zolved.com/Zolved%20Remote%20Control.exe
View computer - http://www.zolved.com/Zolved%20Remote%20Control%20Viewer.exe

Allows online collaboration, desktop sharing, and remote PC access. No registration required and no login. Uses UltraVNC to make remote connections.

Other free remote support tools

TeamViewer

Show computer - http://www.teamviewer.com/download/TeamViewer_Setup.exe
Viewer - http://www.teamviewer.com/download/TeamViewerQS.exe

Allows remote control of computers, screen sharing, file transfer, chat ability, and is secure. Have to install TeamViewer software. No registration required and no login.

LogMeIn

Remote desktop sharing. Access remote computers by installing a client software onto each machine. Works on servers and desktops. Free registration required.

Yuuguu

Remotely access your PC or MAC also. Works well through firewalls. Free registration required.

CrossLoop

CroosLoop easy to use, requires each party install the CrossLoop software onto their computers. Uses 128-bit encryption and allows for file-sharing.

SkyFex

SkyFex allows remote watching and remote control in real time. Does not require additional software installation works transparently through NAT and Firewalls. Only works on Microsoft Internet Explorer.

Dimdim

Remotely share your desktop features web conferencing, collaborate, share voice, video, slides and whiteboard. Free registration required.