I wrote a post a long while back about the use of Groove as an intra-company bulletin board. Well, we started having some problems with Groove back in late 2005, especially with synchronizing (auto copying of updated files up to people's computers when they login). It would pretty much lock up the computer and was overall a pretty big resource hog. Now I still like the features and think it's a pretty cool overall product, the performance characteristics became a barrier for us.
Early this year, we moved to using Jotspot. It is a fairly simple Wiki product that is easy to get started on and easy enough to use by the entire organization. JotSpot is Joe Krause's (of Excite and Long Tail fame) company and I believe they were bought by Yahoo just a couple of months ago, so their longevity is fairly assured. You can edit docs as wysiwyg or use the simple wiki markup for editing, easily create pages, and even create mini-apps by importing spreadsheets. There is a fairly low startup cost as well. I believe it's $99/year for a small group (<=10 users) and 100 pages.
We've used it a lot for asynchronous brainstorming and keeping large grained tabs on projects.
So far it's the best/easiest tool I've found for an intracompany interactive bulletin board. If you haven't used wiki's before I would highly recommend giving them a try and this is a great place to start.