Hello,
I've tried all solutions, from zip, syquest drives, external harddrives etc. The best and most useful has been my Yamaha cd-rw 8-8-24. It performs flawlessly. In addition, cds can be read everywhere and are easy to store, have pretty good capacity and are the cheapes option around. the only downside is the size of the unit itself. Not very portable at all. There are smaller, portable ones but they're also more expensive and slower.
The hard drive options is good too, but cd seems more reliable still.