Today I was lamenting the slow death video tapes undergo due to frequent use. I have a series of videos originally taped from the Discovery Channel in the mid 90's that are on their last legs, so I did a search to see if they were available for sail anywhere and found some good stuff.
The series was titled The Secret Life of Machines. I found the web site for the series (http://www.secretlifeofmachines.com/). On the site they have clever cartoons derived from the shows, which you may be able to use even if you never show the videos. The show focused on describing how some modern machines came to be and how they work.
Anyway, I followed a link to Tim Hunkin's website. He was the host of the show. Tim provides links to a site to download torrent files for all three series of TV shows.
If you've never seen this show it's a lot of fun and definitely worth a look. Granted, some of the "modern technology" is a bit dated, but there is still some good science here.
Side note: Torrents are used to download files from Bittorrent, which is a P2P file sharing network. You'll need a program to do that, I've used uTorrent and Azureus in the past. I should also point out that not all things you download through bittorrent are legal (and not all files you download are illeagal eaither). As these torrents are being provided by the show's creator I assume they are leagal.