Our partners at EconEdLink have some material that you might find helpful for your lessons on savings. You can search the Thinkfinity.org site or go directly to the EconEdLink page to search their lessons specifically. Go to: http://www.econedlink.org/lessons/ for lessons and http://www.econedlink.org/interactives/ for interactive components to accompany a lesson.
If you have access to a bank or credit union in your area, they may also have materials for teaching about savings. Credit Union's tend to be very responsive to the communities they serve in this way and may have many resources to help you out. Checking their web sites or giving them a call may give you additional options.
Good luck and let us know what you decide to use and how it works for you!