Iomega makes both 1-gigabyte and 2gb Jazz drives, which are fast and easy to work with. The drive, which can back up to 40 megabytes a minute, plugs directly into the iMac's USB port. Another option is an external hard drive. As with the USB devices, it's a portable external drive that can easily be moved from one PC to another. The company also makes drives that plug into the USB port or PC card ports on laptop machines in capacities ranging up to 14 gigabytes.
CD writers are another potential backup system.
Finally, there's the Internet. A number of services will let you back up your files to offline servers. The advantage of these systems is that they're easy to use, don't require any special equipment and, by definition, provide you with an off-premises backup that is secure even if something disastrous happens at your place of business.