TeamViewer

TeamViewer - Simple, Fast and Secure Desktop Sharing.

Desktop sharing has never been easier: With TeamViewer you will be able to connect to the desktop of a partner anywhere on the Internet.

TeamViewer also works in the other direction: Show your own desktop to a partner over the Internet and demonstrate your own software, solutions and presentations.

• Remote Control without Installation
  With TeamViewer you can remotely control any PC anywhere on the Internet. No installation is required, just run the application on both sides and connect - even through tight firewalls.
• Remote Presentation of Products, Solutions and Services
  The second TeamViewer mode allows you to present your desktop to a partner. Show your demos, products and presentations over the Internet within seconds - live from your screen

Protable Version
http://www.teamviewer.com/download/portable.aspx