JSTOR is a massive online archive of academic journals, virtually all of which were behind a subscription wall. (JSTOR's been quite arbitrary about locking up its content; some of the papers it hosts are available at no cost elsewhere. For example, these papers from the Proceedings of the National Academy of Sciences USA are freely available on the PNAS website but not on JSTOR.) Two days ago JSTOR opened up part of its database by giving free access to nearly 500,000 old articles. From JSTOR's announcement:

I am writing to share exciting news:  today, we are making journal content on JSTOR published prior to 1923 in the United States and prior to 1870 elsewhere, freely available to the public for reading and downloading. This includes nearly 500,000 articles from more than 200 journals, representing approximately 6% of the total content on JSTOR.

The announcement also refers obliquely to two related recent events — Greg Maxwell releasing a slice of old JSTOR material on the Pirate Bay (previously discussed on Less Wrong) and Aaron Swartz being charged for illicitly downloading papers from JSTOR en masse:

I realize that some people may speculate that making the Early Journal Content free to the public today is a direct response to widely-publicized events over the summer involving an individual who was indicted for downloading a substantial portion of content from JSTOR, allegedly for the purpose of posting it to file sharing sites. While we had been working on releasing the pre-1923/pre-1870 content before the incident took place, it would be inaccurate to say that these events have had no impact on our planning.

JSTOR makes similar comments in its FAQ for the new initiative too. There's also a two-minute video demo.

(Via MetaFilter. Another recent LW discussion of academic publishing.)