Here are some useful links for some of the topics I mentioned en passent in the discussion of Chalmers:
Twin-Earth Thought Experiments at the ever useful Field Guide to Philosophy of Mind site.
For a fuller discussion of semantic externalism, I especially like the Stanford Encyclopedia of Philosophy article Narrow Mental Content
Here is the paper by Chalmers and Andy Clark, The Extended Mind that I mentioned. Also at Chalmers site there's a link to the Philosophical Zombies site.
Here is Searle's Chinese Room paper, a.k.a. "Minds, Brains and Programs" and here's a powerpoint I made of it.
"Brains in a Vat," is the earlier article by Hillary Putnam I mentioned.