encrypt your own data, then use any service you want. Win.
Basically. I essentially use ssh. I think that is as cross-platform as humanly possible. sFTP to my own server. Encrypted through OpenSSL or TrueCrypt as necessary. Most of the stuff is not encrypted, because the files are pictures I am posting to Facebook or my server.
Google, Dropbox and Amazon are fine for normal files.
Any encryption program and any cloud drive is good enough.
Anything encrypted and not cloud based is going to be a bit of a hassle.