TwitBird Pro is a full-featured iPhone Twitter app that supports landscape view for tweets and the inline web browser. As they claim in the App Store description, landscape view is available on pretty much every screen of this iPhone app. If you are a fan of typing or web browsing with a wide screen on the iPhone, this is the twitter app for you!
Tweetings Mobile is a secure, full-featured Twitter app for iPhone and iPod Touch that supports Push Notifications. Although the development company appears to make primarily Windows software, their venture into the iPhone space is very commendable. Tweetings Mobile can do everything Twitter.com allows you to do, including posting tweets, following/unfollowing/blocking users, reading @ mentions and DMs, and public timeline searching. Some notable features: