Admin Navigate to Macintosh HD/Library/Preferences/SystemConfiguration/
Copy com.apple.airport.preferences.plist
So long as you are using 10.5.7 on the other computer, it will copy the wireless networks information.
In order to copy the credentials (WEP Passwords, etc) you will need to navigate to:
Macintosh HD/Users/yourusername/Library/Keychains/
Copy login.keychain
On your other mac, import the keychain by going to the Finder, clicking on the Go menu and selecting Utilities. Open up Keychain Access and go to the File menu and select Add Keychain…
Then select the login.keychain that you just copied and viola, you have imported the keychain.
Make sure you delete any sensitive information from the base keychain before copying it to another computer!
Finally, replace the com.apple.airport.preferences.plist in Macintosh HD/Library/Preferences/SystemConfiguration/ with the one that you just copied.
