How can I make a usable backup of the site on CD? The client would like to archive off a copy of their drupal 7 site every 6 months or so. By archiving, they are referring to copying the site (in a usable format) onto a cd.

What are some of the options for doing this?
The Backup and Upgrade module can be used to schedule automated database backups. One of those backups, combined with the codebase, gives you a full backup of the site. If this is to be burned to a disc every 6 months, I wouldn't bother automating anything - the time investment won't be worth the future time savings.