"Open-access (OA) literature is digital, online, free of charge, and free of most copyright and licensing restrictions.
What makes it possible is the internet and the consent of the author or copyright-holder."
From Peter Suber's Very brief introduction to Open Access.
Learn more : Open Access and Scholarly Publishing
The majority of the journals listed here are peer-reviewed. All are free to the public, and do not charge any publication fees for authors.