Dropbox can be used as a central bare repository when you have multiple work stations.
The setup steps that I follow:
~/project $ git init
~/project $ git add .
~/project $ git commit -m "first commit"
~/project $ cd ~/Dropbox/git
~/Dropbox/git $ git init --bare project.git
~/Dropbox/git $ cd ~/project
~/project $ git remote add origin ~/Dropbox/git/project.git
~/project $ git push -u origin master
You can just clone ~/Dropbox/git/project.git that you have associated with your Dropbox account or have shared this directory with people. You can perform all the normal Git operations and they will be synchronized to all your other machines automatically.