Teamviewer

Forget Hamachi (earlier blog), Teamviewer is much more refined as a remote access tool. Plus, it's portable and cross platform. I can access my Ubuntu desktop or my wife's Window machine from another Linux or Windows PC anywhere without having to reconfigure my firewall. Hell, I can even do a pretty decent job controlling either machine from my Android phone using their app. Plus, it's portable and even the full version can be put on your keychain. And to help others, you can simply send them a simple small executable via E-mail and all they have to do it is run it without having to install anything.

For the one time support user, it generates a random number each time a username, and a random number for the password. They'll have to tell you those numbers over the phone to let you access their machine. Plus, they see what you're doing (and will hopefully learn). When they exit the program, nothing's left running and there's no access.

It's free for personal use. The company seems reputable enough and the link is encrypted, but it's not open source, so who knows if there's any back doors or vulnerabilities. Needless to say, I don't leave it running unless I know I might need access.