NeDi showcase (a better than commercial solution)

The video above is a showcase of the implementation of NeDi.  This is a great tool to not only view the configuration and topology of a network but can assist greatly when troubleshooting a network.  It is a tool that can answer many of the checks in the network troubleshooting checklist here.  As a network management tool it far outstrips 99.2% of commercial offerings currently out there.
It is available as a open source download and runs on the sniff of an oil rag (or the server equivalent - an HP Microserver - with 8GB of RAM).  Here is the server below:

Download the software here or for a more comprehensive list of tools look here.