Type in a number, click “Connect”. That’s how easy it is to connect two computers together using the CrossLoop software. According to their site:

CrossLoop is a free secure screen sharing utility designed for people of all technical skill levels. CrossLoop extends the boundaries of traditional screen sharing by enabling non-technical users to get connected from anywhere on the Internet in seconds without changing any firewall or router settings. It only takes a few minutes to setup and no signup is required.
Just a few days ago, my business friend Mrinal Desai informed me of the new software so i said I’d check it out. Crossloop provides a simple solution for connecting to computers quickly. The software is positioned as a simple alternative to netmeeting. I personally found the software to be easy to use, but somewhat slower than alternative net conferencing software. On the other hand, the software is free whereas the web conference software I use costs $49 per month. I highly recommend using the program for anyone who needs a quick way to connect two computers for providing quick technical support.