One of my favorite features with the Beta 2 update to Visual Studio 2005 was the ability to export your Class Diagrams as images. Yes, it's simple but you won't believe how useful it's been lately sucking code in from a 2003 project, automagically creating the Class Diagrams (thank you Microsoft!) and exporting it to communicate to the development team.
Dmitriy Vasyura of the Visual Studio Class Designer Team has an excellent post on the ClassDesigner's WebLog that goes into great depths on preparing the diagram, making use of comment shapes to annotate the diagram, documentation scenarios, and of course exporting the images. Check out the post here for more info.