For work I run Windows 7, but do my work in an Ubuntu virtualbox. That file I backup locally, to a connected USB drive, and to a NAS. The OS I don't backup at all since everything I need data-wise is on a corporate server.
For my personal stuff, I have a mixture of a large media library, and my wife's business files. The entire system gets backed up nightly (via rsync) to a primary terabyte USB drive. And then I back it up again to a different secondary terabyte USB drive. The business files (her accounting data, website source code, etc.) are additionally backed up to an offsite cloud backup service.
Every year I buy a new terabyte drive and make it the new primary backup drive. The old primary backup drive becomes the new secondary backup drive. The old secondary backup drive gets DBAN'd and sold on ebay. That way my primary backup drive hardware is never more than a year old, and secondary never more than 2.
My media library backups run the risk of a local disaster; fire, etc. But I can afford to lose all that and just be sad about it, but no big financial loss. My wife's business stuff is backed up locally + offsite for obvious reasons.