Prezi is a cloud-based presentation software that opens up a new world between whiteboards and slides. Users can collaboratively develop presentations.
SlideShare is currently the world’s largest community for sharing presentations, documents and professional videos. Once you sign up for an account you may upload your own presentations and also add comments or questions to others work and save as favourites, thus creating a useful library to refer back to. Sharing options enable viewers to share your presentations to Twitter, Facebook and LinkedIn. You can also embed presentations in to your blog as below.