There are many real-time document collaboration services available on the Internet but none of them give you the fuzzy feeling of having full control of the fruit of your labor.
You can work on a document from your desktop/laptop by running Etherpad in a virtual machine and make it available for collaboration over Internet using PageKite.
The steps:
Run the following commands:
git clone https://github.com/nifgraup/pagekite-tklpatch
apt-get install tklpatch
tklpatch-apply / pagekite-tklpatch/
confconsole
Your document is off the Internet the minute you turn off your virtual machine. Turn it back on and continue from where you left off.