I just discovered PPT Remote and love it (and I have zero affiliations with the developer -- I'm just excited about this!). It lets you remotely control a PowerPoint presentation on a laptop or desktop via either Wi-Fi or Bluetooth. Here's the cool part: you can set it up to show your speaker's notes on the phone while the slide is on the screen, OR show the current slide on both the phone and the screen, OR (and this is the coolest) show the NEXT slide on the phone. Free, in the market. I was just about to plunk down $40 for a Powerpoint remote for my laptop. Now, no need.