Tom Tague presented Open Calais to our Semantic Web Meetup in L.A. last night. If you need to tag your content, or pull semantically meaningful data AUTOMATICALLY, use Open Calais, API key needed. There is a WordPress plugin called Tagaroo. I wish I could install it here but it doesn’t work on wordpress.com (yet?).
Just for fun I’m going to run this post through the Open Calais demo and see the results. Watch for it in the comments.