Sync the Sites folder
For local web development, I want the Sites folder on both my Macbook Pro and iMac to be synchronized using Dropbox.
The first step is to create a symbolic link (symlink) in the Dropbox folder that points to the Sites folder. The article How to sync folders (or files) that exist outside the "My Dropbox" folder explains how to do this on the first machine, but doesn't describe what needs to be done on the second.
Justin Blanton provides the necessary clues on the Dropbox setup steps for second machine. Basically, you'd need to create symbolic links in the Dropbox folder on both Macs almost simultaneously. Very importantly, the user name on both computers need to be the same.
In my case, I just had to make sure to quit the Dropbox application on both of my Macs. I then took my time to create the symlinks on both machines. After I had created the symlinks, I then launched Dropbox.
My Sites folder on both Macs are now perfectly synced, and I'm free to work on either computer, safe in the knowledge that new, updated and deleted folders and files will be perfectly mirrored.