SlideShare is a beta social network site for sharing slide shows. You can have shows with audio attached, or just plain one that you click through.
I’m not really sure why slide shows should be shared, especially if they don’t have an audio track. This strikes me as a corruption. Slides were meant to enhance (not replace) talks. Now we have the slides without the talks they support. Tufte described the problems with shoehorning ideas into slides in The Cognitive Style of Powerpoint. If slides are a crutch, SlideShare is a pilgrimage spot where you can see the crutches left by others.
Of course, there are uses for SlideShare. I guess you can put you slides up there so you can access them for a presentation. And trading decks of slides has become a way of proving you know something.