Dropbox allows you to synchronize outside your /home directory? Maybe if you re-point it to a specific location? I haven't tried that.
I read in a article that there is a way to use symlinks to grab extra, individual files from outside your /home to either your Dropbox or Ubuntu One folder so it is synchronized even though it isn't in your /home.
I think it was a HowToGeek article, and I don't remember which service they were talking about (doesn't mean it won't work for the other too).
You right! Dropbox don't allow files from outside your /home. I'm using 4shared