I just did a quick scan of the various VoIP security blogs and links, and things are pretty quiet. Here is a link to a post on VoIPSA, from Shawn Merdinger, that shows google searches for topics like "VoIP security" are way down.
Brian Lutz and I have been updating the SANS course on VoIP security. This is a six day course and absolutely the best course in the industry on this topic. The course will be officially available next year. We are planning a presentation of the course in November or December down in San Antonio. This will be a great opportunity to particpate early in the course, with the actual authors.
I will post more information about the course when I have more details. If anyone is interested in more information, please comment on this post or send me an email at firstname.lastname@example.org.