Aspose.Slides for Java is a Java component for manipulating PowerPoint presentations. It doesn't require PowerPoint and supports export to PDF, embedding and linking of audio and video frames, slide cloning, thumbnail generation, and presentation features, the ability to extract text from a presentation, and more.
Encours.org is a teleconferencing system that works directly in your Web browser. It has shared slides that are visible to all, an integrated audio system with recording, "laser" pointers for lecturers, video replays of the presentation, and a chat interface with the audience. It can be connected to a phone server.