I've been a long-time user of LogMeIn's free remote assist.  As the resident computer help desk in my family I've installed the LogMeIn client on all the not-so-tech family computers.  My mom, mother-in-law & wife all have this installed on their machines.

This way when I get the call as long as their PC has an internet connection I can access their machine and fix it.  It uses NAT traversal, so it doesn't require any router configuration. This is a great product. Now LogMeIn moves to the smartphone world. Their IT helpdesk product LogMeIn Rescue now offers the helpdesk the ability to access a user's BlackBerry handheld and take complete full control of the device.

What makes this product cool is that the user doesn't need any preinstalled software on the BlackBerry.  The helpdesk simply provides the user with a PIN for the session and on the browser the BlackBerry user goes to logmein123.com enters the PIN and POW! full control is handed to the IT helpdesk.