on our site we have an "announcements" section on the profile page (first page user sees when they sign in) so we can post something there. We usually will like the announcement to a longer story (similar to a blog post) where users can comment and provide feedback. We also have public feedback groups on our site, so we'll often post the updates there as well as let some of the more active users know directly. - Julio from Experience Project (http://experienceproject.com)