I come from an Open Source background. We share things. We make them available for others to use, adapt, improve upon, or turn them into something else entirely. Therefore, I usually share the slides for my talks. For this, I used to use SlideShare.
While SlideShare is already useful just for looking at slides, you will actually have to register to get the most out of it. Not only will you be able to upload your own and download other people's slides (if the author allows it) but you can also follow speakers and be notified when they publish new presentations. In other words, it's yet another social network. In fact, since SlideShare is owned by LinkedIn, it is part of a social network that you may already use.
