I recently had my hard drive go bad -- good news, most files backed up -- bad news, I still don't know how to back up my address books in Netscape -- lost all my emails and addresses soooooo... if I was supposed to send you something and didn't, please contact me again.
(Note: this does not apply to the workshop DVD people whose addresses I still have on the sign up sheet.
Assuming you're running on a PC, Netscape usually stores the user data (emails, address book, etc) in the folder "\Program Files\Netscape\User". Within that folder is a subfolder for each user you defined in Netscape. To back up the user data just copy everything in the user's folder. You don't need to save the contents of the Cache folder - it's large and just contains a cache of recently visited webpages. If you need to restore the user's data just copy the whole folder back to the "\Program Files\Netscape\User" directory.