Do any of these programs/services allow one person (me) to serve as the host but which do NOT require the guests (everyone else) to download software or register on a website to participate?
The purpose is so that they can view my desktop while I demo software, but avoid the hassle of having them install software or register to use it.
BitsDujour is going to be offering a discount on something called "Online Desktop Presenter" (http://www.bitsdujou...index.aspx?review=15
I have not tried the software, so I'm guessing at how it works. But from its description it looks like it simply automatically takes a screenshot every second or so and posts it to a website. The guests just go to a webpage that periodically refreshes the image.
If that's what's happening, then you'd get the requirement that no registration or client viewer installation is required. The drawback would be that any quick screen changes or animation would be lost or not look good. But if you're doing a powerpoint presentation (and don't put a lot of fancy transitions in it), it might work pretty well.
The nice thing about it is that all you need is a web server (and even there, Infonautics says "Use of free web space if no own web server is available", so I think you may not even need your own web server)
You'd have to rely on other things to support the clients being able to ask questions or such For small groups, teleconference would work well.