Audio & Video

Sounds—including music, narration, and sound effects—and short video clips can also be embedded in instructional content. Audio adds a whole dimension of pacing, timing, and reality missing in visuals alone. Whenever you use audio or video, provide the learners with an on-screen cue (image or graphic) that an audio or video clip is available.
An example of audio might be to have the teacher speaking words used in the terminology of a course. This allows the student to gain proper pronunciation skills that would have been picked up in a regular classroom.

Original video can be difficult, to host and expensive to create but it is relatively easy to link to online video sources, such at Youtube.com. Be aware that Youtube links often change, so you will need to check them at the beginning of each offering.

Also see:

Top 10 Things About Images on the Web  (pdf format)