See Doron Zeilberger's page where he provides the proposals for several of his (approved) grants:

http://www.math.rutgers.edu/~zeilberg/grants.html

By the way, this presentation also could be of some use:

[Writing an NSF Proposal: a PI's and a panelist's perspective][1]


as well as the *Notices* article

[NSF Proposal Preparation: The View of an Ex-Program Officer][2]


  [1]: http://math.ou.edu/~profdev/nsfprop_web.pdf
  [2]: http://www.ams.org/notices/200709/tx070901153p.pdf