You have to have Office Live, which I believe comes with any Office 365 subscription.
You store the PPT on your Microsoft One Drive (Cloud Storage). Set it to public sharing. Open it up it up in office.live.com
Then select, File -> Share -> Embed.
This gives you the necessary iframe code to embed the PPT into a web site. That way, your site users do not need to have PowerPoint installed in order to view your slide shows.
For instance, I am on a system right at this moment that does not have Office at all. But I can still view the slideshows on your site.