[makaio]

After reviewing the options some time ago, I ended up using encfs on top of Dropbox. You still mount and unmount it like Truecrypt or Apple's encrypted disk images, but behind the scenes instead of creating an opaque block device to store the files, the individual files and directories are stored with their names and contents encrypted. I like this method because individual files can be synced (which is the whole purpose of Dropbox), safe syncing does not require unmounting the volume, it can be mounted on multiple computers at the same time, is cross-platfrom, and I think it should be possible to revert individual files to a previous revision (though I've never tried). The main disadvantage, from a security perspective, is that the existence of and approximate size of your files can be easily determined without decrypting. This does not matter for my purposes, but might for some. It is also slightly more complicated to set up, although if you've ever mounted a filesystem from the command line in Unix you should have no problem.

Here is a nice overview of its use on OS X: http://www.packetslave.com/2011/04/21/dropbox-encryption-w-e...