Heard of Slideshare.com? I think this is one, if not the most, popular community slide sharing web site. I actually love it coz chances are, you'll find info that you are looking for from the thousands of slides that have been uploaded.
But wait, a new one was just born. Called SlideSix, it looks like a much simpler site and it is uncluttered. However, it's brand new. Based on my search for Learning 2.0 or Web 2.0, nothing came up.
Maybe, a good site to upload your slides to if you are not keen to have too many other people viewing your slides. Definitely, not the best place to visit if you were looking for presentations. But, who knows what will happen in a year or two.