Already in place for physics (Score 5, Informative)

The arXiv system (www.arxiv.org) already hosts just about every preprint that comes out in high energy physics, astrophysics, and several related disciplines. Access is completely free, and they currently host 400,000 papers. Needless to say, people post there for a reason: it works really effectively to get research results out to the public quickly and efficiently, and as mentioned before, it's totally free for everyone involved. Open access isn't a theoretical question taking place in a vacuum, it's already underway, and it works just fine, and can even coexist with the refereed journal system, as the physics world has learned over the past decade.