See Doron Zeilberger's page where he provides the proposals for several of his (approved) grants and the *reviews* (as noticed by Ben in his comment below) for two of them:

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

For other examples, see 

[SCREMS: The Computational Frontiers of Number Theory, Representation Theory, and Mathematical Physics][1]

(it was awarded: see [here][2])

and the awarded grant proposals by James Propp [here][3] and [here][4].

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

[Writing an NSF Proposal: a PI's and a panelist's perspective][5]


as well as the *Notices* article

[NSF Proposal Preparation: The View of an Ex-Program Officer][6]


  [1]: http://modular.math.washington.edu/grants/screms/
  [2]: http://www.nsf.gov/awardsearch/showAward.do?AwardNumber=0821725
  [3]: http://faculty.uml.edu/jpropp/Quasirandom.pdf
  [4]: http://faculty.uml.edu/jpropp/Entire.pdf
  [5]: http://math.ou.edu/~profdev/nsfprop_web.pdf
  [6]: http://www.ams.org/notices/200709/tx070901153p.pdf