SlideShare lets you upload, tag, and embed your presentations on any web site.
You can upload your PowerPoint and OpenOffice presentations, tag them, embed them into your blog or website, browse others' presentations, and comment on individual slides. It's a great way to share your ideas with others, or to learn from other people. And it's free.
After you upload a slideshow, you can view the small version or go fullscreen (which looks really good), clicking through slides one at a time. Looks like a great tool share presentations.
Slideshare is the work of Uzanto - a small startup based in Mountain View, CA and New Delhi, India. There is more on their FAQ page