From the Bad Science forums I found a link to an excellent video of the Tree of Life. This is taken from a BBC show about Charles Darwin broadcast to celebrate his 200th birthday and the 150th anniversary of the publication of The Origin of Species and was produced in association with The Wellcome Trust.
The video of the tree of life is available in YouTube version, but you can also download a copy for your own use. It’s licensed under a Creative Commons licence so you can use it in your schools as long as you attribute the source and don’t use it commercially.
There is also an interactive Tree of Life which allows you to trace the ancestry of many different creatures and also makes it easy to find the common ancestors between pairs of animals. So if you want to find the common ancestor between Man and Penguin, then you can (something called Amniota, in case you were wondering).
This is a beta version and so will develop over time. Again you can download a standalone version if you want to use it in schools.
Science/Biology teachers who are looking for a resource to use when teaching evolution or diversity of life should definitely check it out. And the creative commons licence means you could even get the students to put it into movie maker (or similar) and record their own narration over the top.