Om has posted a pretty concise preview about VON. I'm heading over and will provide some on the scene coverage as time permits.
I can confirm that xConnect is the company in the peering play Om's talking about and that Vapps is the company, according to my sources doing the conferencing deal with Yahoo. Yahoo's big VoIP cheese Brad Garlinghouse is coming to VON as is Jeff Bonforte, the guy who is making things go over there. I just wish they would have the new Mac client done.
There's also alot of cool things coming from other companies so as the news breaks, the blog army will be there covering in Hawaiian shirts and all.