Default Sources
The default Sources are as follows: (not all may be available on your system)
Applications
Applications - applications in /Applications
Applications (Mac OS 9) - applications in /Applications (Mac OS 9)
Applications (User) - applications in /Users/yourusername/Applications, if you have any.
Running Applications & Processes - fairly self-explanatory and lets you switch between running applications quickly.
Find All Applications - tries to find all applications on your hard drive, irrespective of their location.
System
Configuration
Network Locations - locations available under Apple Menu > Locations. The default action is 'Switch to Location', so this is a speedy way to change your network settings.
User Accounts - allows you to switch between users from the Command Window.
Preference Panes - directly launch individual Preference Panes via the Command Window.
System Preferences (All Users)
System Preferences (User)
System Preferences (System)
Devices
Discs- scans all the mounted volumes (including those in /Network) .
Printers - networked printers.