For corporate video conferencing, we usually have a dedicated “codec” from Tandberg or Polycom. However, we recently ran across this offering from Sony which works well, has nice modular add-ons, supports the latest protocols, and is more economical: Sony iPela PCS-G50. (CDW is a good corporate vendor if you want to simplify purchasing – not the best prices, but decent.)
NetMeeting is a deprecated Microsoft H.323 client. Looks like Microsoft wants to push everyone over to Live Meeting. It’s still included in XP though (START | RUN | Conf), and I guess that you can install it into Vista: http://en.wikipedia.org/wiki/Microsoft_NetMeeting.
We have been using NetMeeting to test H.323 connectivity and to link in remote users. (Multi-site capabilities in the VC codec usually cost more.)
I have come to conclusion that it doesn’t make sense to keep your codec behind a firewall, I agree with this site: http://www.more.net/technical/video/troubleshooting/videofirewalls.html. Basically just turn off the web-interface and other IP services and you should be secure. I have many bumps on my head from H.323 firewall configuration..