Wikipedia's article on Open Access is excellent; it provides a comprehensive introduction to principles and practices "through which research outputs are distributed online, free of cost or other access barriers."
The Scholarly Publishing and Academic Resources Coalition (SPARC), an education and advocacy group that investigates and reports on alternative scholarly communication strategies.
A directory of OA repositories at academic institutions, search engines for the repositories, and links to information and statistics about OA repositories.
The Digital Commons, Our Institutional Repository
What's So Great About the Digital Commons?
The Digital Commons collects, preserves, and disseminates the intellectual work of the Trinity community.
It increases the visibility and impact of deposited works.
It supports authors by helping them retain copyright to their work.