It may also be the case that installing nfs
will be smart enough to also install dependencies like portmap.
It might also be the case that the OP doesn't correctly distinguish between 'not installed' and 'service not running'. My recollection is that Fedora will start up all dependency services for the NFS server by simply starting the NFS server. Try something like (as root):
service nfs start
## .. or maybe
service nfsd start