Two external hard drives for backup. One 8TB to serve as an off-site backup for my Mac Pro (which already has an 8TB internal backup drive), and a new 2TB portable for my MacBook Air was filling up (so its existing backup disk can be an off-site backup, too).
(Mac users: Did you know that Time Machine supports multiple backup destinations? Also, you can encrypt a backup after the fact by removing it from Time Machine -- it won't delete anything -- and then adding it back with encryption selected. It'll add the existing backups and encrypt them retroactively.)
Once they get fiber in my neighborhood, and thus have really high upload speeds, I may consider an online backup, too.