The most basic is to a stack of floppies. Iomega, maker of the Zip drive, also makes Bernoulli cartridge systems, but only about ten Mackers in the country use them. Syquest also makes a 135-meg drive to compete with the Zip, but stay away from it. Too much of a me-too product, it will probably disappear in 6 months. Finally, there are tapes.
Tape backup is the least painful to use, requiring no attention at all, except to change tapes.
This is the method of choice if you have more than a few hundred megs of data on your drive, and want to be absolutely sure that your data is backed up every day. Extra money buys hardware compression, more storage, faster copying, etc. This is the best solution, especially if you are backing up a network. The QIC units have been available on Intel boxes for some time, and are just now becoming available for Macs. APS offers the only ones I have seen, but this may change by publication date.