Publishing your work in an open access journal makes it visible, searchable, and more accessible to other researchers: it increases usage and impact, and evidence shows it boosts citations.
Publishing your work in an open access journal, which may take the form of a fully open access journal or hybrid journal (an extra fee is paid to a traditional journal to make your particular article open access), results in many of the same benefits as self-archiving. Those who previously could not access your work if it was published only in a traditional journal, due to costs of subscriptions or access difficulties, can now easily gain access. Your work can reach more potential readers, which results in greater use and impact.
Jeffery, K. G. (2006).Open Access: An Introduction. ERCIM NEWS, 64.
Swan, A. (2010). The Open Access citation advantage: Studies and results to date. Technical Report, School of Electronics & Computer Science, University of Southampton. http://eprints.ecs.soton.ac.uk/18516/
Suber, P. (2007).Open Access Overview: Focusing on open access to peer-reviewed research articles and their preprints.http://www.earlham.edu/~peters/fos/overview.htm