If you often find yourself cutting-and-pasting charts or tables generated in R into PowerPoint or Keynote, you might want to take a look at Slidify. Created by R user Ramnath Vaidyanathan, Slidify is an R package that allows you to use R Markdown to define the slide content and automatically embed R output. This is especially useful if the source data for the R analysis might change as you're developing the slides: rather than cutting-and-pasting the changed outputs all over again, you can just re-run the Markdown document and get your slides updated instantly. The slides look great, too: just open the generated HTML file in a browser to see slides like this:
(That's a screenshot, not the actual slide deck. Once you click through, click to the left or right of the slide to move through the presentation. It would be nice to be able to embed a Slidify deck in a Web page, but I don't see a way to do that just yet.) Slidify slides can also have interactive features, like quizzes and this carousel display that allows the viewer to cycle and compare several related charts.
Here are some instructions on getting started with Slidify. It's as simple as installing the slidify package from GitHub, writing a document in MarkDown, and then using the publish function to deliver the completed slides to GitHub (with a GitHub account, and git must be installed), Dropbox or Rpubs for others to see.
Ramnath Vaidyanathan: Slidify