CommonCraft is one of those sites that is so simple, yet so useful. The creators use an easy-to-follow "felt-board-like" video montage to explain tricky Web 2.0 concepts. The one featured below explains "in plain English" how blogs work. It would be a good way to introduce the application to students or interested teachers.
The site also has a number of other easy-to-follow explanations as well.
Video: Web Search Strategies in Plain English
Video: Social Media in Plain English
Video: Podcasting in Plain English
Video: Twitter in Plain English
Video: Online Photo Sharing in Plain English
Video: Social Bookmarking in Plain English
Video: Social Networking in Plain English
Video: Wikis in Plain English
Video: RSS in Plain English
