I've used ZFS under Linux for 5 years now for exactly this sort of thing. I picked ZFS because I was putting photos and other things on it for storage that I wasn't likely to be looking at actively and wouldn't be able to detect bit-rot until it was far too late. ZFS has detected and corrected numerous device corruption or unreadable issues over the years and corrected them, via monthly "zpool scrub" operations.
I have been backing these files up to another ZFS system off-site. But now I'm starting to look at other options because it's looking like I can begin doing it more cheaply than even my free hosting of a box I bought can provide.
Amazon Glacier reduces the cost of S3 storage by an order of magnitude, making 2TB of storage cost around $20/month. For a backup copy, it's hard to compete with this, even just buying a USB drive to stick somewhere... You do have to be careful about recovery though, they charge based on peak download speed (a very weird pricing).