I have always thought images back up the points of a writer and break up the text, but then I’m an Art Historian, so images are my stock in trade. I have always joked that I went into Art History because I only like books with pictures. I think Ko and Rosen also make some good points about making things easier and more interesting for students. To me, that goes back to the student-centered learning that we all want to achieve. I think that often, when we create a class in a CMS, we try to throw all of the information at the students at once, and forget to make it accessible. Formatting your information in such a way as to make it interesting or fun for students to read is something that should be a priority when we lay out our classes, which I will admit to forgetting at times.
I have used Glogster in the past, and I like the way you can put text, audio and video together, but, and this is a big BUT for many of us, they are moving to a pay site. Although I recognize they need money to support the platform, it is challenging for those of us who adjunct at multiple schools to pay the annual fees for everything. Also, as Rob also pointed out, The Edublog Awards show how to do something similar in blog format. I also link or embed a number of the videos from Khan Academy in my classes, as they are generally short and easily accessible to students (in addition to my own screencasts).
Using Html in your course or blog can also be helpful, as it often makes it easier for students to access things like a syllabus. Here, though, you can also link to a Google doc that you have saved as a webpage. Personally, I need to explore the use of html a bit more.