In Slideshare's (http://www.slideshare.net) most viewed presentations ("views"), many were in other languages, and some were wallpaper rather than slideshows. So, this is an interesting place to look, but not the most effective way to search. The same is true for "favorites" and "featured." There is a wide variety of topics that are covered here!
Choosing the "Education" link narrows things down a bit. I noticed that some presentations aren't really meant for us strangers to view and understand. I think some members of Slideshare have loaded presentations here that they will need at a future date. So, without their speaking while showing the slideshow, we don't really understand it. When I clicked on most viewed education videos of all time, I saw several on Web 2.0!
Searching can be time-consuming, but I noticed that when entering my own search term, I could choose the language for my results. I finally chose a narrow enough search that I found some useful results. I chose this presentation on the Dewey Decimal Classification System (DDCS) that I could use with my students:
I liked this presentation because it was simple and could be used with young students. It covers pretty much exactly what I say when I teach the DDCS, but the added visuals are nice.
Slideshare is definitely useful if I am giving a presentation. I can save my slideshow and then just access it at the time and location of my presentation (assuming they have Internet access). In the classroom, I could use slideshows I find at Slideshare (like the one above) to enhance lessons I teach. I could also creat my own slideshows and save them to Slideshare. Also, when students are doing research, they could create slideshows as their presentation method and share them via Slideshare.