There is a tool that is very promising, it is called ScribTeX, The free collaborative LaTeX editor. Its description is giving

Welcome to ScribTeX, the online collaborative LaTeX editor. ScribTeX allows you to work on LaTeX documents from anywhere with internet access and share them with your friends and colleagues easily. You can:

* Create and edit LaTeX documents and automatically render them to PDFs;
* View a complete revision history of all your files;
* Keep your documents private, allow people of your choosing to view or edit them, or publish them to world;
* Use BibTeX to keep track of your references and include them in LaTeX documents;
* Upload images and include them in your LaTeX documents;
* Create custom style files and use them in your LaTeX documents.

Hope this can help many of us doing better collaborative work.