Prezi for a couple of months, but finally used it in class today. In my middle school Social Studies class, I teach a Holocaust unit coinciding with my students' reading of The Diary of Anne Frank in Language Arts. My topic today was Ravensbruck, a women's concentration camp in Germany where I visited in 2008. My Prezi, Support and Comfort in Ravensbruck, supplemented our conversation and set up a following analysis of art by Ravensbruck survivors. The Prezi took me about 15 minutes to create (but again, I've done some experimenting previously). Mine is very simple, but there are lots of more complicated visual effects that you can build in.
I love Prezi's intuitiveness on both the creation side and viewing side. Its strength is that it's not locked into a linear structure, but you can still use the "Path" function to create a narrative. I like that you can choose from several color/font schemes, ranging from somber to splashy, so it can be appropriate for almost any content. A Prezi can be used to supplement an in-person lecture or presentation, or it can be designed to BE a self-contained, complete presentation online. Prezi has free educational licenses for teachers and students.