Dropbot is a simple tool that allows you to easily sync things into Dropbox without any hassle. Simply right-click the item, and sync it, right-click again, and unsync it.
This service allows you to right click any set of files or folders and choose "Symlink to Dropbox". This will move the selected files/folders to ~/Dropbox/Dropbot and then place a symlink in the original location of the file.
This is the opposite to the above, if you right-click a Dropbot symlink you can select to unlink, which will remove the symlink and move the symlinked file/folder out of dropbox and into the location of the symlink.
(In OSX) Simply open the workflow files and agree to install the services when prompted. The options "Symlink to Dropbox" and "Unlink from Dropbox" will appear in the right-click/control-click menu when selecting files in the Finder.