The main and most permanent venues for open access are repositories and journals.
There are two main types of Open Access journals,
Harnad, S. and others. (2008). The Access/Impact Problem and the Green and Gold Road to Open Access: an update.
Free access and rights to re-use content.
Further reading about this ongoing discussion:
These myths about open access are all FALSE.
(Content from Isaac Gilman (2009), Open Access in 15 Minutes (or less), used under a Creative Commons Public Domain certification.)