Since CrashPlan uses blowfish-448-cbc-sha1 (a weird choice) and may (I'm uncertain on this) have ability to push configuration changes from remote, I've considered that possibility, because of CrashPlan's "unlimited" offer.
Unfortunately, it's barely usable due to recovery issues. You can't mount CrashPlan as a filesystem (well, without ton of reverse engineering), so that's not an option unless you're satisfied with all-or-nothing recovery without possibility to pick and restore just certain files of interest.
A middle ground there that would work for restore of particular files is to use ecryptfs/encfs without encrypting filenames. I think ecryptfs at least knows how to do this. Then you can download the file with the proper name, but the contents are encrypted and decrypt them locally.
You could probably also hack up something to figure out locally what encrypted filename corresponds to what regular filename and go fish for the encrypted filename in CrashPlan. It will probably be clunky though.
That's if you only rely on CrashPlan-provided encryption, which is certainly not a cream of the crop.
We were talking about eCryptfs/encFS-encrypted copy, where filenames are (usually) encrypted. That means navigating around names like `l00Dqf,A49VqDd8AveLMrbBE` or `qR,bmE-73cA2H6wOxZxlKSwD`.
Unfortunately, it's barely usable due to recovery issues. You can't mount CrashPlan as a filesystem (well, without ton of reverse engineering), so that's not an option unless you're satisfied with all-or-nothing recovery without possibility to pick and restore just certain files of interest.