Colocating the members of the team, Developers and Customers (including Testers), does wonders for increasing the communication on a project. And the trust.
[http://www.possibility.com/Cpp/SoftDevOfficeLayout.html The Ultimate Software Development Office Layout] by Todd Hoff
[http://www.agileadvice.com/archives/2005/08/optimizing_a_te.html Optimizing a Team Room] by Mishkin Berteig
[http://www.sciam.com/article.cfm?chanID=sa017&articleID=D9058A4E-E7F2-99DF-36023504D1E43BD6&ref=rss The Science of Team Success] by Steve W. J. Kozlowski and Daniel R. Ilgen (From the June 2007 issue of Scientific American Mind)
"Organizational behavior expert Kyle Lewis of the McCombs School of Business at the University of Texas at Austin found that the development of a team's ability to access distributed knowledge required face-to-face interaction. In groups that communicated exclusively by phone or e-mail, this skill did not emerge."
[http://conway.isri.cmu.edu/~jdh/collaboratory/research_papers/ICIS2002_Proceedings.pdf Shared Mental Models, Familiarity, and Coordination: A Multi-Method Study of Distributed Software Teams] by J. Alberto Espinosa et al.
[http://hdl.handle.net/1721.1/1866 A field experiment to improve communications in a product engineering department : the non-territorial office] by Thomas J. Allen and Peter G. Gerstberger.