Adam Dachis from Lifehacker has the skinny on a new Mac app that is designed to do the work of creating symlinks for a folder into your Dropbox for you:
MacDropAny is pretty straightforward. First, you run the app and choose the folder (outside of your Dropbox) that you want to sync. Once selected, you’ll be asked where you want to place a symbolic link to that folder. You can choose any location in your Dropbox. For the last step, just name your symbolic link and it’ll be placed in your Dropbox. To add another folder, just run MacDropAny again.
The app is on the official Dropbox wiki and is free. Can’t argue with free applications that make things easier for common folk, but this process was already pretty simple for a user with any sort of savvy.