In my mind, ArXiv is the best example of using the internet to tear down some very counter-productive walls. ArXiv postings have essentially replaced print journals as the place physicists and mathematicians go to catch up on the most current work in their fields. More importantly, papers posted there are available to anyone willing to download a PDF. (...) Meanwhile, nothing similar exists for Humanities, and the most current research in fields like Classics languishes behind online paywalls.