I've been using Tweetie on my iPhone more and more. It's come to play a significant role in my daily life, a role three years in the making that has steadily supplanted email. Like the snailmail cards I still get from older relatives, email messages are becoming more and more scarce. Formal correspondence (often just a poor substitute for a phone call IMHO) is about all email does for me these days, although I've found new uses for it through Posterous and other web applications. On the media side of things, I've found Qik, an on the fly video + streaming video application, to be my new best friend.