====== OS X ======

==== Find the gateway address ====

  route -n get default

It is not the same as GNU/Linux's route -n (or even ip route show) but is useful for checking the default route information. Also, you can check the route that packages will take to a particular host. E.g.
  route -n get www.yahoo.com

The output would be similar to:
  route to: 98.137.149.56
  destination: default
  mask: 128.0.0.0
  gateway: 5.5.0.1
  interface: tun0
  flags: <UP,GATEWAY,DONE,STATIC,PRCLONING>
  recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
  0         0         0         0         0         0      1500         0

IMHO netstat -nr is what you need. Even MacOSX's Network utility app(*) uses the output of netstat to show routing information.