TweetDeck, arguably the most popular desktop app for managing all things Twitter, just landed in the App Store. It's free. And it's a winner.
Like its desktop counterpart, TweetDeck for iPhone and iPod Touch relies on customizable columns: one each for things like replies, direct messages, searches, and friends. You swipe back and forth between the columns using your finger, then tap one to bring it to the fore.
(Is it heresy to say the interface reminds me a bit of the Palm Pre's "cards"? Well, sorry, but it does.)
Needless to say, the app lets you tweet, retweet, send direct messages, e-mail tweets, and mark tweets as favorites. It also supports multiple Twitter accounts; each one gets its own column(s).
Too bad you can't set up separate batches of columns for each account, as you can easily end up with column overload.
TweetDeck does let you create user groups for following friends. You can also search, save your searches, and tweet photos by way of Twitpic or YFrog. It'll even shorten URLs, though I couldn't figure out how to make this work.
(I'll fess up to being stupid if someone will explain the feature in the comments.)
If you're already a TweetDeck user, you'll be glad to know the app syncs with the desktop version, and will even pull in your Twitter account settings if you've already configured them.
Though TweetDeck did crash a couple times during my tests, there's no doubt in my mind that it'll quickly become a favorite among Twitter users. Its slick interface and thoughtful feature set have already earned it a permanent spot on my iPhone.