New NSF Proposal Policy Guide (Including Data Management Plan Info) Available Online

Starting in January, all grant applications to the National Science Foundation must include a
two-page-maximum “data management plan” (DMP) for the retention and sharing of digital
and physical data generated from the research process.

For the most up to date requirements for National Science Foundation funding, see the NSF's new Proposal and Award Policies and Procedures Guide, January 2011 as well as their Frequently Asked Questions (FAQs) On Proposal Preparation and Award Administration, November 2010.
 
Plus, UW-Madison now has a Research Data Services Web site, which can help you with writing a data plan, as well as with managing and sharing your data!  For more information, contact digitalcuration@lists.wisc.edu. 

Perhaps you've not yet identifying which grant(s) to which you plan to apply?  Try Finding NSF Funding (Search or Browse functions available).