Announced over on the Twitter Blog is the new mobile version, web look, and Tweetdeck look.
We'll be rolling out the redesigned Twitter over the next few weeks. You can see it immediately on the just-updated versions of mobile.twitter.com, Twitter for iPhone, and Twitter for Android. You can get early access on your computer by downloading and logging into Twitter for iPhone or Twitter for Android. We're working on updates for other apps, such as Twitter for iPad, and will share news as they become available.
You can hit fly.twitter.com to see more.