Google has launched Powerpoint Preview for Gmail.

Gmail users can use Google’s Powerpoint competitor through a View as Slideshow feature.

Gmail Powerpoint Preview (image by Google Blogoscope)

From Mashable

When you receive an email with a Powerpoint attached, you can view the slideshow in a new window - no need to download and open in Powerpoint itself.

Gmail already provides options for opening Word and Excel files in Google Docs and Spreadsheets.

Link via Mashable