Instructables is a site filled with “how-to” slideshows and videos. There are tons of new sites that have these kinds of instructional videos, but Instructables is the first one I’ve found that actually focuses more on step-by-step instructions using still images with captions. All of the “instructables” (which is what they call them) are user-generated.
I definitely would not use the Instructables site to have my English Language Learner students create “how-to” slideshows. The creation process does not appear to me to be particularly user-friendly and is overly-complicated. I’ve reviewed many other slide-show web applications that are easier to use, like One True Media. You can find many more on my Examples of Student Work page under Student Slideshows.
However, Instructables is a great place for students to see examples of what a good instructional slideshow would look like. They can look through a variety of them, and then just go to another site to create their own slideshow.