If you have attended many presentations for which the speaker used PowerPoint slides, you have probably seen some presentations that made good use of PowerPoint and too many that did not. For a humorous look at bad PowerPoint, watch Life After Death by PowerPoint, a video by comedian Don McMillan.
Another video, Le Grand Content, makes an almost surreal examination of "the omnipresent Powerpoint-culture in search for its philosophical potential. Intersections and diagrams are assembled to form a grand 'association-chain-massacre', which challenges itself to answer all questions of the universe and some more." See a review at Presentation Zen.
Finally, check out SlideShare, a fabulous site for sharing your presentation slides or viewing what other presenters are doing. You can also use SlideShare to embed your presentation in a blog or website. Search by topic tag, or browse the Latest, Most Viewed, Featured, Most Commented, Most Favorited, or Most Zinged. Enter the World's Best Presentation Contest, or vote on your favorites, by April 23.