You can find the connectors in electronics stores and online for prices ranging from about $10 to $35. I used a no-name MHL adapter and cable that cost $10.50.
There's no software to load, and for now, you need to power the MHL cable using an AC adapter. (The MHL standard includes a provision for the adapter to draw power from the projector or TV it's attached to, but as yet very few devices support this function.) The good news is that the MHL cable can use the phone's power adapter, and it simultaneously charges the phone it's plugged into.
After plugging one end of the MHL cable into the phone and the other into the projector's HDMI cable, the connection is automatic, and the images show up on the big screen at 1280-x-720-pixel resolution. Regardless of how you orient the phone's screen, the big-screen image stays right-side up, but you do have to keep the phone from going to sleep.
Using the MHL cable and a Mitsubishi projector, I gave a presentation using the OfficeSuite Pro app without a hitch.
Of course, MHL is still an emerging standard, and only a couple dozen smartphones support it today, but that number is expected to increase over time.
Via a presentation remote control app
Another strategy is to bring the presentation on a USB flash drive or email it to someone at the office where you're headed, then load it on a laptop there. Once it's all loaded on a computer that's connected to the projector, you can control it from your smartphone with a presentation remote-control app.
I used Signal Beach Software's ShowDirector PowerPoint Remote for Android, which works with Microsoft PowerPoint running on a Windows PC. There's a free trial that limits you to showing 10 slides, but the full app costs only $5.
After loading the ShowDirector server software on the computer connected to the projector, I fired up the Android app to wirelessly connect the Nitro HD phone to the PC. I used Bluetooth to link them, but the software can also use a Wi-Fi connection.
The program's interface has buttons for moving forward and back through the slides, as well as rearranging their order. I could also adjust the volume as I roamed around the room. In other words, I was in control of the show.
What about other mobile platforms? Windows Phone smartphones come with PowerPoint Mobile included, and iPhones can use Keynote ($10) to show a presentation. When it comes to BlackBerry devices, though, you'll need a separate box called BlackBerry Presenter that costs $200 and plugs into a projector or a TV.