If you are backing up or archiving to DVD or other non-ACL'd media, encryption is a desirable option. Sadly OSX doesn't have any good encrypted zip possibilities. Imagine if you backed up your profile to DVD, someone got hold of the backup and now has access to all those banking web sites with saved passwords etc. OK so they would need to get your keychain password, but there is a better way.
What we can do is to create an encrypted Disk Image using Disk Utility.
Go to File>New Disk Image from Folder
Select the folder you want to turn into a disk image.
Give it the correct options ie encrypted at 256bit, and what you want to call it
After a few seconds you get the box to apply your password
And then the disk images process continues. Be warned that 256 encrypted images even for small amount of data can take a long time to create. The folder I've used here had 800Mb of photos in in and it took about 20 minutes