Preferred Remote Access system

I use TeamViewer, which is free for personal use and works with Windows, Mac OS X, Linux, Ubuntu, iPhone, iPad, etc. It's very secure and quite simple to set up and use (no messing around with ports), which comes in handy if providing remote support to those who aren't very computer literate. You can talk them through the setup on their end and be connected to them in less than a minute. I prefer it over LogMeIn because it includes free file transfers between computers, a feature I use frequently.