Comment Truecrypt + Dropbox (Score 4, Informative) 200
I use Truecrypt's encrypted drive containers in my local Dropbox folder. The file sync'd to Dropbox is encrypted when the sync occurs, so that is all they ever see. Because Dropbox does a binary diff of the file and only uploads the differences which makes syncing large encrypted files feasible.
I've seen some chatter that Truecrypt may have been compromised - Bruce Schneier and Snowden use it so I'll trust in their judgement.