You might want to take a look at the Voicethread for Educator's ning. I have used it with students for math and computer class. I have identities for each student. They take turns coming up to a main computer and adding responses. I've had them take digital photos and draw images with a simple program called Kid Pix. Some students do not like to record their voice. You may want to give them a choice of either typing or recording information.
My students are often reluctant to read aloud or be recorded. I teach reluctant readers so I can understand their hesitation; they are used to being the "bad" readers of the class.
In the case of read alouds, the students really have no choice. We popcorn read every day; every student must read at least once before the popcorn reading is opened so that any reader can participate. After about three days of class, students have figured out that in my class reading is required and that everyone is there to help them.
In the case of recordings, students have the option of going into another room to be videorecorded. By the time I get to videorecordings my students are used to being recorded with iPods. We have several weeks or oral fluency where the students record themselves reciting poetry and listen to their own recordings. Video is just the next step up.
They also know that others may see/hear their recordings. I don't allow negative comments but positive comments are encouraged!