One of the most difficult social media concepts to explain is how to make use of an RSS feed with a feedreader. I have met very web-confident folks that look at me cross-eyed when I talk about blog subscriptions.
The Commoncraft team took on the challenge with their RSS in Plain English video. Google asked them to take it one step further with their custom video, Google Reader in Plain English.
This one comes in significantly shorter than most of the other videos, yet it still captures the je ne sai quois that their other works have. Enjoy!