From the about page:
SlideShare is a business media site for sharing presentations, documents and pdfs. SlideShare features a vibrant professional community that regularly comments, favorites and downloads content. Content also spreads virally through blogs and social networks such as LinkedIn, Facebook and twitter. Individuals & organizations upload documents to SlideShare to share ideas, connect with others, and generate leads for their businesses. Anyone can view presentations & documents on topics that interest them. The site is growing rapidly with over 17 million monthly visitors.