If you want to webcast, you should take a look at Sorenson Broadcaster. You can download a demo. (OS9)
It costs $199 and works great if you have tthe bandwidth.
If you want to video conference there isn't anything else I know of that will work with a dv camera. They all seem to need dedicated webcams, although firewire ones are available.
Try a search on versiontracker with the term 'firewire', 'webcam' or 'webcast'