One thing about DMing 4e that has always driven me to distraction is the sheer ball ache of putting encounters together in a format that works at the table. Of course, WotC has a monster builder, but the export function is still poor. And the compendium is great, but again, putting together groups of monsters is unnecessarily difficult. Enter the iPad.
You can access the compendium via the browser, Safari. Don’t worry about apps, this is perfectly good enough. Find the monster you want to include in your encounter. Now grab a screenshot. You do this by holding down the home button and pressing the power button. The screen will flash white, and an image is put into your photos folder. Repeat with each monster you want to grab.
Now go to your photos an open up a new folder for your encounter. Add the photos in that you just grabbed by ticking them. Done. At the table you can open up the folder and swipe through the monsters back and fort. It’s incredibly tactile and really easy. As its on an iPad it takes up very little room behind your screen. In fact, with your adventure on the Notes app, you’ve just cut down on your DM footprint by at least half.
I know there’s all kinds of dice rollers and initiative trackers, but they’re for another day.