This issue has a few articles on global software development. Some touch on agile softare. One of the articles was a little odd, implying you needed duplicate role positions on both sides (which I can somewhat believe), and that cost is 150% of nominal (which seems unintuitive). (I'll admit I just did a quick skim of these articles, so perhaps I'm misinterpreting conclusions.)

There's also an article, "Building Objects Out of Plato: Applying Philosophy, Symbolism, and Analogy to Software Design." If you're interested in the XP idea of metaphor, this may give you another take on it.