Unfortunately, neither the web interface nor the native app of UbuntuOne provide an option to list all shares. There is nonetheless a command line tool called ‘u1sdtool’. With the help of this tool you can quickly and easily make out which folders are shared. Just open a terminal emulator of your choice and execute the following command:

$ u1sdtool --list-shared | grep -oe "\(/.*\)*"

The attached ‘grep’ restricts the output to the paths.