Slideshare is a website for uploading and sharing presentations. It is similar in look and feel to sites like YouTube and takes advantage of many of the same types of features including tags, discussion, and tools for embedding (via Flash) presentations into blogs and web posts.
For example, below you will find my slides from my talk at TechForum Seattle that took place on November 2, 2006. I did the slides in Keynote, and Slideshare only accepts presentations in PowerPoint (.ppt) or OpenOffice (.odp) , so I had to convert my Keynote presentation to PowerPoint before uploading. It sure beats saving a PowerPoint presentation as html, and it also allows for discussion and community.