Introductory video
A completely unbranded video with a vanilla version of WPMU 2.6 that you can use as a support video for new bloggers on your site - choose to either download the video as a .swf or simply embed it (code available to members under the 'Installation' tab).
This video is Flash, under 5MB and 640px wide x 480px high (for ease of embedding in a blog format).
This video gives a 5 minute introductory walk through to new users and is an invaluable way to get peopel started.