Freeware for Testing Video Networks
Wireshark - A must for your networking toolkit. Wireshark is a cross platform software protocol analyzer - and you cannot beat the price: Free. FaultLine will analyze the transport streams in Wireshark capture files.
VLC Media Player - Probably the best and most reliable media player out there. In addition to playing back a multitude of video files, you can use VLC to watch the video on your digital video distribution network or act as a video server.
The SLAC Network Monitoring Tools page has a huge list of tools used for Network (both LAN and WAN) Monitoring. Many are free to use.