Directory structure for cross-platform phonegap project
Its actually quite easy with Git and Submodules. The phonegap wiki referenced above is indeed a bit slim so I actually went ahead and implemented a solution that configures xcode & eclipse project.
See the link on my blog post: Phonegap project structure using git submodules
If you don't want to use Git submodules, there is a Symlink solution as well which doesn't care if you use Git or SVN.
http://www.tricedesigns.com/2012/02/16/linked-source-files-across-phonegap-projects-on-osx/
there's a writeup (looks like a first pass) on the phonegap wiki that explains how to use a git submodule. to supplement that entry, i also did a writeup on using the svn:externals property. my only thought on symlinks is that it's something people have to setup as opposed to getting them intrinsically from the source control repository. not really a problem, but it is a logistic to the setup when you switch computers or get additional devs on a project. i'll be taking the svn:externals route until i find something better.