You must have heard of flashmeeting. Picked it up only now.

Website says: "The simple one-click video conference! It works in a web browser running the Flash 7 plugin!"

This is experimental, and requires registration. Sidebar reads: "Registered users book meetings using a simple web form. The system automatically returns to you, the booking confirmation and 'ticket' you need to pass on to the people you want to join the meeting, to give them access." Here's the link.