This is a video of Mac OS X's Intro videos. It is a part of a series of Leopard videos. Mac OS 8 intro is available here: (Not included because it's so long)
UPDATE: Unfortunately Snow Leopard's final intro video is the same as the Leopard one... Hopefully next time Apple will do something more exciting... If you want to see the Leopard/Snow Leopard intro the way it was meant to be (in HD), check it out here:
All of these intros were created by Apple, and I don't own the copyrights to any of this.