I have a
lot of stuff, spread across a variety of different computers and my phone.
So I use
Syncthing (free, open-source, runs on almost anything) to "sync" all of my important files to just one computer:
my NAS, "Fox", with 96TB of HDDs in (72TB usable).
And then I have a subscription to
CrashPlan, who allow
unlimited backup space because they charge
per computer, not
per gigabyte. And I only have one "computer" (it's just one with massive hard drives that all of my others back up to!).
I'm investigating other options, though, and I'm not opposed to paying per-gigabyte. A few hosting companies have Amazon-S3-compatible storage now (so it's possible to use the standard tools to sync with them) but cheaper prices (especially if you're willing to say "if I need to restore a backup, I don't mind paying you to get the tapes from the shed and that taking a couple of hours"), so I'm considering that.