I've made class diagram for Direct2D library. Enjoy :)
By the way, yEd is a free editor for all kinds of graphs, including UML diagrams like this. It may not allow you to enter list of fields and methods in classes like StarUML or Visio do. It may not allow to freely draw shapes like Inkscape or OpenOffice Draw do. But for creating, editing and arranging graphs of different kinds of nodes, interconnected with different kinds of links, it is really great. I especially like the way it snaps all positions and sizes to the neighbour nodes. Commands for automatic arranging of nodes, called Layout, also look impressive. Plus it supports different file formats, including XML-based, so you can easily generate such file and then open it in yEd to visualize some data.