On the 20th June, a team of mathematicians released a book on Homotopy Type Theory, written collaboratively over 6 months with GitHub and Latex. The content is of no direct interest to me - but the collaborative method of writing, and using git to work simultaneously on a large Latex project certainly is.
Discussion of using git + latex on HN, including touching upon methods to be able to merge simultaneous edits (latexdiff etc.): https://news.ycombinator.com/item?id=5914586
GitHub repository (quite a nice Latex Makefile, and interesting to have a look at the chapter contributions vs. time): https://github.com/hott/book
The combination of ‘web service’ version control such as GitHub, and Latex seems like a really powerful method for efficient collaboration on paper writing (well, and science in general!). For those of us who are not mathetmaticians or pure physicists, convincing our collaborators to leave the comfort of Mark Changes hell & emailed copies of this_great_paper_version55_JMFedits.docx may be the challenge.
If your paper is too confidential for open editing, http://bitbucket.org offers private repositories on free team accounts to academics (all you need is an academic email), and you can always install git-as-a-web-service (such as http://gitlab.org/) software on a lab machine.