This is a very long video but it addresses some useful tips and tricks how to make nice slides in powerpoint. It starts with a ballroom presentation or a presentation without bullet points. This will get you updated on death with powerpoint and how to create slides for different audiences. The biggest part is on how to create those slides. This topic is usually not covered in the books on presentations.
Related blog post:
Presentations for Physicians
Thanks to Moving at the Speed of Creativity