Robin Good: Memplay is a free web service which allows you to collaboratively upload images, video and audio files, and then to edit these into a final video.
Images and other media files can be imported directly from your computer as well as from your Facebook galleries.
Once you have uploaded all of your audio, video and image resources you can use the web-based video editor to assemble easily your final video.
Memplai provides integrated effects, transitions and video templates.
Free to use.
Getting Started: http://memplai.com/Home/Tutorial
More info: http://memplai.com/
Via Robin Good