Answer by
LeheckaG (1826)
"Off-line" options:
- flash-memory cards
- recordable or re-writable CD/DVDs
- external hard-disk drive(s)
- magnetic back-up tape?
- paper?
"On-line" options:
- mirrored-pair(s) of hard-disk drives
- on-line photo "sharing"/storage services: Flickr, Google, Kodak, PhotoBucket, ShutterFly, ...
- on-line backup/storage services: aDrive, Carbonite, iBackUp, iDrive, JungleDisk, Mozy, XDrive, ...