Know the basics of what you are using:

Get the Grand Tour.

Know some basic troubleshooting procedures.

Quick Links

• Migrating data from Windows to the Mac
• Change your account password: X.5, X.4
  
• What version do you have?
• Force quit an application
• How to burn a CD or DVD
  
• Find the warranty information
• Basic Security information
• Working with Screen Shots
• Quick tips (short videos)
• Find out how...
  

Finder

• What is it?
• Working with Files & Folders
• Learn the Desktop
• Know the Dock
• Understand the Menu Bar
  
• Typing in another language
• How to do general maintenance
  

Printing

• X.6: Printing 101
  
• X.6: Included printer and scanner drivers
  
• X.5: Included printer drivers
• X.5: Setting up network printers
• Ordering printers

Apple Mail

• Account Settings
• Differences between Entourage, Apple Mail and Piratemail
  
• Set up Out of Office Replies
• Disabling Out of Office Replies

Safari

• Setting the default home page
• Setting the default web browser
• Customizing the Tool Bar
• Turning on/off the pop-up blocker

Networking

• Cisco Clean Access Agent for the Mac
  

XCode

Can be installed from the Mac OS cd/DVD or its free from the Apple's Developer Website.