Copilot 2.0

Copilot from Fog Creek Software is one of the most impressive software services I've ever seen. It lets you easily and effectively connect to virtually any other computer over the Internet and control it remotely (with permission)- and it works regardless of whatever security and firewall settings are in place at either side of the connection.

I've used it several times to troubleshoot problems on people's computers in a number of situations, and it's simply amazing.

Version 2.0 was recently released, and it's got some impressive new features, including Mac support.

Cool stuff.