Well, I went and did it. I bought a drobo - backup/storage robot to back up all of our photos and other files. I'm quite happy I did - I feel much more secure having redundant backups, especially of our photos. In addition to the drobo, I also bought a portable external hard drive to be used as an offsite archive. I intend to back up to that once per month and then store it offsite in a safe deposit box.
First lesson of the drobo - high speed USB 2.0 definitely makes a difference over regular USB. To be frank, I wasn't really aware that my iMac had both a high speed USB port, and a "regular" USB port. So, first question is why did they even put in USB 1.0 ports if 2.0 were available? The new iMacs have 4 USB 2.0 ports + 2 more on the keyboard, and 1 firewire400 and 1 firewire800 port. Serious envy.
Once I got all the geek-gear from Amazon, I made my first back up to the stand alone hard drive, and by luck, plugged that drive into the high speed USB port. The back up of 190GB of data took a couple of hours (4 maybe?). Then I set up the drobo, and started the same back up process to it. But I'd plugged the drobo into a regular USB port. I turned it on around 8:00 p.m., and by 8:00 the next morning it had only backed up 30GB onto the drobo! Clearly something was not as I'd expected. After checking all the manuals to ensure it would be OK, I paused the backup, put the drobo in standby mode, updated the drobo firmware, and then plugged it into the high speed USB port. And in 1 hour it's backed up twice as much as it completed in 12 hours on the "regular" USB port. So for future reference - high speed USB absolutely makes a difference over regular USB!
Next stop, Radio shack to see if I can get a proper cable to connect the drobo firewire800 port to the firewire400 port on my iMac. This is entirely feasible, I just need the right cable. Once I have that, then future backups should be even faster. The drobo came with a cable to connect from firewire800 to firewire800, and firewire800 didn't even exist when I bought my iMac, so it definitely doesn't have a port for it. Have I bored you to tears yet? Who's still reading? Raise your hand.
Anyway, I'll get some pictures of all this soon (cause one of you is still reading and cares....). Fun with technology.