One of my all time favorite books on building effective presentations is Presentation Zen by Garr Reynolds. I have recommended this book to students and colleagues for years. Reynolds also has a blog by the same name.
This first link below will take you to a 2005 blog post where he discussesWhat is good presentation design. The second link is a more recent post where Reynold features a really effective visualization technique as presented by Hans Rosling. The Rosling video can be linked to directly here.