Using the PACE acronym:
Primary: Laptop harddrive
Alternate: Dropbox, one 500Gb portable harddrive
Contingency: SkyDrive, Google Drive, one 750Gb portable harddrive
Emergency: one 1Tb external desktop harddrive
And, I guess my iPod kinda acts like a backup storage for my music if I need it to. =]
I really don't want to lose my data, so, it seems to average out about once per year, I add another place to store my data. The storage units I use are typically bought Black Friday every year.