Haiku Deck is a fantastic tool for designing slideshow presentations. The best aspect of Haiku Deck is the built-in Creative Commons image search tool. That tool makes it easy to find high resolution images to match the message of each slide in your presentation. Over the last year I’ve had a handful of occasions on which used Haiku Deck to find images and design slides before dropping them into Keynote. On the same track, Haiku Deck recently published directions for exporting Haiku Deck to PowerPoint. That option is available in both the iPad and web app versions of Haiku Deck.
And if you want to import PPT or Keynote slides into Haiku Deck, you can find those directions here.