Voice Thread is a cool tool. I like the way it is built around sharing images and our thoughts about those images. In some ways it is an iconic program for digital natives, since it invokes visual and verbal literacy, rather than simply textual literacy. I have no proof, but I would guess that the folks who type their comments are older than the folks who record their comments. This program also has the virtue of being simple to use.
I could see using this program in my professional life for prayer services, rather than in classroom settings. I found an example of the Stations of the Cross created by an elementary teacher and her students, with homemade drawings and personal voice overs. The format allowed the students to integrate the symbolic dimensions of faith with modern technology. I think it is a terrific tool for engaging students in their faith on a personal level and allowing them to express the results in a medium that is comfortable for them.