"The Public Library of Science (PLoS) is a non-profit organization of scientists and physicians committed to making the world's scientific and medical literature a freely available public resource."

See http://www.publiclibraryofscience.org/ BrokenLink
 
See http://www.plos.org/

Also see OpenContent, BudapestOpenAccessInitiative, CreativeCommons, and OpenArchivesInitiative.