A DMPTool is now available that can guide you through the creation of a DMP for use with projects funded by NSF and other US agencies. The DMPTool can be customized for particular fields and institutions, and was developed by the UC system, UC San Diego Libraries, DataONE, the Smithsonian Institution, and other organizations.
Since January 2011, NSF has required that proposals include a two-page maximum supplementary Data Management Plan document. This describes how to disseminate and share research results over the course of the proposed project. You can see the relevant documents at the NSF policy and requirements website, including those specific to Directorates, Divisions, Programs, or other NSF units.
NSF's agency-wide guidance for preparing a DMP is very general. Applicants are asked to describe the types of data to be collected, standards to be used for data and metadata, policies for access and sharing (including protection of privacy), policies and provisions for reuse, and plans for archiving and preserving access to data.
Some individual directorates and programs within NSF have more specific guidelines. What is considered appropriate data management is left largely to individual disciplines via the peer review process and program management.
One of the primary mechanisms NSF uses to ensure post-award compliance has been the requirement that PIs and co-PIs describe the availability of research products in subsequent grant proposals.
You can review a summary of data management and sharing policies for US federal funding agencies.