As much as PowerPoint continues to be a popular tool for presentations, there are other tools which are as easily accessible to present slide shows. These are some which I have come across and offer the possibility to include images, multimedia and more:
With igniteCAST you can upload videos, images, music; it's a great tool for learners to create digital stories, share courses, quizzes and surveys.
SlideStaxx also creates slideshows which you can then embed in blogs. One feature is how it helps you collect social media from different sources, pulling them together in a slideshow.
BrainShark lets you create, share and track how effective a presentation is. I'd also like to point out a great screencast by Russell Stannard, explaining how to use BrainShark, in a step-by-step presentation.
Zentation combines videos and slides to make presentations, making it useful for webinars and webcasts.