Video Conferences system work well with Asterisk?

I will set up Asterisk for telephony, maybe voice conference, and use MySQL to store user data and configuration files, but I also want to have video conferences system work together.
Does anyone knows the video conferences system that I can set up to take advantages of the running Asterisk system?
Thank you very much!

i have tried using windows messnger 5.1 with 2 users talking while seeing
their faces. it work great for two users at a time