I've used the yEd Graph Editor from yWorks to create similar diagrams. It's a free desktop application and runs on Windows, Unix/Linux, and Mac OS X. It's a WYSIWYG application, so, you can easily import, create, rearrange, and export many types of diagrams. Have a look at the Gallery of diagrams submitted by other users. It should give you an idea as to the types of graphs/diagrams you can create. For example: