Dropbox/Copy.com & Truecrypt

I have a partition that contains all my personal stuff, which is mounted at boot under /home/myuser/foo. I would like to synchronize it on the cloud via Dropbox or Copy.com, but I don't trust them, so I have to encrypt the data in some way. As I understood, it creates a "volume" when opened, and the data is clear only in ram, which is great. The problem is that this volume is seen as a single file by the Dropbox/Copy.com client, so when I change something, as little as a text file, it will attempt to upload again the whole encrypted "volume". There is some way to encrypt my data and upload it in security?