Synchronize a folder outside the default Dropbox's directory

[CONTEXT]
You want to synchronize a folder with Dropbox, without move that folder to
the default  Dropbox's directory
[HOW]
Create a symbolic link from the folder that you want to synchronize to the Dropbox directory, for example

$ ln -s /path/to/folder/to/sync ~/Dropbox

The permissions of the files or folders should be (at least) owner:r/w, group r/w, and others: r
-rw-rw-r-- 

[SOURCE]
http://www.dropboxwiki.com/tips-and-tricks/sync-other-folders

How to synchronize Multiple Dropbox Accounts in your computer

[CONTEXT]
You have multiple accounts in dropbox. (Assume that you have alredy install dropbox on your computer).

[WHEN]  
You want to synchronize all your dropbox account files in your computer at the same time.

[HOW]

• Create the alternative folders for your additional account, for example

         $ mkdir ~/.dropbox-mte
           $ mkdir ~/dropbox-mte

• Run from a terminal the following command

        $ HOME=$HOME/.dropbox-mte /usr/bin/dropbox start -i

• Configure your account and make as default directory ~/dropbox-mte

• Create a file to launch the new instance of the dropbox deamon for example,

            DropboxAltStarter.sh

           #!/bin/bash
           HOME=$HOME/.dropbox-mte /usr/bin/dropbox start

• Executable permissions 

           $chmod 755 ~/DropboxAltStarter.sh

• Include DropboxAltStarter.sh in your starter.

"Go to System -> Preferences -> Startup Applications. Click Add and          include the following:
Name: 2nd instance of Dropbox
Command: /home/Username/DropboxAltStarter.sh
Click Ok."

  
[SOURCE]
http://www.maketecheasier.com/run-multiple-dropbox-accounts-in-mac-and-linux/2010/05/24