Tweetie – For iPhone – multiple accounts, favorites, deleting, following, trends, location, re-tweets, photos and more.
TwitterBerry – A mobile client for posting updates to Twitter on BlackBerry devices.
Sharing via Twitter
TwitPic – If you have a Twitter account then you already have a Twitpic account, just login to Twitpic with your Twitter username and password and you are all set to upload and share photos.