In past releases when Revit Structure touted the ability to miter steel beams and Revit Architecture couldn't lots of Architecture users were mighty annoyed. Revit Structure 2009 has enhanced the join process and options AND Revit Architecture get them TOO! The Beam Join tool will be found on the "Tools" Tool Bar next door to the Edit Wall Joins button.
Here's what some beams look like after playing with them.
Since the video doesn't seem to be working in this post you can see it HERE