I have almost 20GB of 'digital assets' (mainly photos) now. As my day job is as a storage engineer I know all to well that hard disks can fail, and I would be devastated if I lost them all so I keep them on a pair of hardware mirrored ATA hard disks that are not my main work machine.
I used to save them to CD-ROM, but this is time consuming and I had one too many CD failures (luckily I burn two copies of everything, and leave one at work).
If my house burns down, or if one of the local volcano erupts (apparently due in the next few hundred years, great photo op though!) I will loose all my data, as I don't have an offsite anymore, I am thinking of a removable drive.
How does everyone else protect their data? I have heard too many horror stories about people keeping all their data on a single disk and loosing it all to not take this stuff seriously. I hope I am not being too paranoid!