GPG - Chapter II.C.2.j, Special Information and Supplementary Documentation contains a clarification of NSF's long-standing data policy. Under the new NSF policy, however, all proposals due on or after January 18, 2011 must include a data management plan that describes plans for keeping and sharing of the products of research. Where a plan is not needed, a page is still needed asserting the absence of the need for such plans.
Fastlane will not permit submission of a proposal that is missing the Data Management Plan. The Data Management Plan will be reviewed as part of the intellectual merit or broader impacts of the proposal, or both, as appropriate.
See the NSF website for discipline-specific guidance and frequently asked questions. http://www.nsf.gov/bfa/dias/policy/dmp.jsp
The MIT Libraries have developed data management resources that can be found at http://libraries.mit.edu/data-management/plan/write/