LFT (Layer Four Traceroute) is a sort of "traceroute" that often works much faster than the commonly-used Van Jacobson method and goes through many configurations of packet-filter based firewalls.
MarcoPolo uses fuzzy logic and rule-based matching to make educated guesses as to your current location, and it automatically switches to the correct network location. It can match on attached USB devices, as well as assigned IP addresses.
Route Tracer is an application that allows you to trace the route over the network between two systems, listing all the intermediate routers a connection must pass through to get to its destination. It provides the physical geographical locations of network servers and routers. It shows the actual route path on both the three-dimensional globe and the flat map, and calculates the distance between your computer and intermediate servers.
With RouteSplit you can add a static route, test it and optionally install a launchd startup script in your system in order to preserve the route settings after reboots.
WhatRoute is designed to find the names of all the routers through which an IP packet passes on the way from your Macintosh to the destination host. It can display these paths in tree form, or on a map of the world.