World of Teaching is a website of free power point slide shows for wide variety of subject areas and grade levels. The World of Teaching homepage features the most recent additions. All of the slide shows are organized by subject area. Each slide show is available as a free download. I would like to see World of Teaching add a preview option so that you didn't have to download each file in order to view the content.
Applications for Education
World of Teaching could be a great website to have up your sleeve when you don't have time to build a slideshow. World of Teaching's slideshows could also be good resources to look through for ideas for creating your own slideshows.
Two similar websites that I've previously written about are Pete's Power Point Station and Power Point Palooza.