"Open access (OA) literature is digital, online, free of charge and free of most copyright and licensing restrictions."
Peter Suber, Director, Harvard Office for Scholarly Communication
Open Access Resources and Initiatives
Open Data is research data that is freely available on the internet; permits any user to download, copy, analyze, re-process, pass to software or use for any other purpose; and is without financial, legal, or technical barriers other than those inseparable from gaining access to the internet itself
(from SPARC Open Data).
Open Data Resources