Basics: Scrolling Vertically

Scratch veteran Archmage has written a wonderful tutorial about how to make platforms that scroll both horizontally and vertically, as in the movie below:

You can read his tutorial at http://wiki.scratch.mit.edu/wiki/Scrolling_Platformer_Tutorial.

You can see a sample project using these techniques at http://scratch.mit.edu/projects/archblogger/312838.