APP NAME: Twitter (formerly known as Tweetie)
WHAT IT DOES: Brings Twitter to the iPhone, letting users tweet and keep up with their tweeps on the go. (If that makes no sense, you probably don't need the app.)
GENIUS FACTOR: The official Twitter app was easily the favorite of The Daily Beast's panel of experts. Fans who first encountered it as Tweetie, an independent offering in the crowded field of iPhone Twitter apps, paid $2.99 to keep connected. Then Twitter itself gave Tweetie the ultimate vote of confidence—acquiring the app, cutting the price to free and renaming it to just plain Twitter. When you first play around with it, the app rewards experimentation—you'll soon find that a quick swipe here or a tap there can get you to nearly any function in a hurry. Marco Arment, the creator of Instapaper and the lead developer at the red-hot Tumblr blogging service, applauds the app for "pioneering new interfaces while retaining iPhone-like familiarity and ease of use."