SlideShare is a great free web based service that allows for you to upload your slideshows (or pdfs) to make a presentation slideshow that your viewers can play. You can make your slideshows open to the public or you can keep them private and invite certain people to view it. You also have a comments feature so you can get feedback from your peers. SlideShare also allows for you to sync up audio with your slides. If somebody likes your presentation or you would like to feature it in your website or blog, you are able to embed that slideshow into a webpage (Blackboard course) or blog or share it in other web 2.0 social services like Facebook.
All you need to do is sign up for a free account to get started. To learn more about SlideShare, click on the link below: