Video clips are a great way to bring the "real world" into your classroom.

You-tube is great and has many clips, however these do need to be checked through carefully for content.

Here are some other sites that have educational clips:

http://www.teachersdomain.org/
http://www.teachers.tv
http://www.teachertube.com

Magic School Bus videos online:
http://www.veoh.com/browse/videos.html (search for magic school bus)
27 episodes online! From Bees to Dinosaurs to Bridges.