In February of 2013, the White House Office of Science and Technology Policy (OSTP) issued a memorandum directing Federal agencies that provide significant research funding develop plans to make the published results of federally funded research freely available to the public within one year of publication and requiring researchers to better account for and manage the digital data resulting from federally funded scientific research. Among other requirements, the memo stipulated that researchers receiving federal grants for scientific research develop data management plans describing how they will provide for long-term preservation of, and access to, scientific data in digital formats resulting from federally funded research, or explain why long-term preservation and access cannot be justified.
For more information, the following sites maintain lists of federal agency data management guidelines:
requires that data underlying published research be accessible and open immediately.
requires that data, software, and tangible research materials are made available to enable other scientists to reproduce and extend the results of publications.
requires data that is needed for independent verification of research results be made freely and publicly available in an AHA-approved repository within 12 months of the end of the funding period (not required for some early-career awards).
For more information, Carnegie Mellon University Libraries maintains a list of US private funders public access mandates & policies.