I try out a lot of Twitter apps on my mobile devices and one of my favorites on Android has been Seesmic. Today, they launched an iPhone/iPod touch version that has some new cool service integration, including Evernote. The new Seesmic for iPhone also includes support for Facebook, Ping.fm, MySpace, Tumblr, Flickr, and more so you can post to multiple accounts at the same time.
The Seesmic Dashboard also lets you configure multiple pages of spaces and customize the app to your liking. There is no version yet for the iPad, but I imagine it will be launched eventually. The Evernote integration lets you store messages and updates to your Evernote account and since it launches Evernote for iPhone you can edit the note while you are there too.
I was a bit disappointed that Seesmic didn't provide this for Android at the same time since I use my Google Nexus One much more than my iPhone, but then I read the Evernote blog post and realized you simply tap and hold on a Tweet, choose Share, and then select Evernote to get this functionality too.