Purchase a copy of Symantec Backup Exec, 2 external hard drives, and a network storage device (Buffalo TeraStation is recommended). The network storage device can be set up to obtain an IP address via DHCP and can be accessible to all users on the network. Direct Backup Exec to save the backups to the network storage device. Create a second set of daily backups to save to these external hard drives. This was you can perform daily backups one of the external hard drives one week, and then plug in the other and take the full one home. Alternate this process weekly for the external drives.
You can substitute tapes for the external drives but I am not too fond of tape backups.
