See Doron Zeilberger's page where he provides the proposals for several of his (approved) grants:
http://www.math.rutgers.edu/~zeilberg/grants.html
For another example, see
(it was awarded: see here)
By the way, this presentation also could be of some use:
Writing an NSF Proposal: a PI's and a panelist's perspective
as well as the Notices article