Mac Lounge is a Mac desktop twitter client application that shares a similar UI to iTunes and its iPhone counterpart.
Mac Lounge requires Mac OS X 10.5.
This is an early beta (*), and some things just don't work yet. For instance, you can't delete tweets or remove Twitter accounts once you've added them to Lounge's account switcher.
It's actually more like an alpha version, but most users don't know what that means.
One of Lounge's most important features is not fully enabled yet: iPhone Lounge and Mac Lounge will synchronize various kinds of meta data, so the transition from your Mac to your iPhone and back again will be seamless.
We're currently testing this on the Mac. iPhone Lounge users will be able to join in once verson 1.1 hits the app store.
There are various other cool features we are working on for both iPhone Lounge and Mac Lounge. Stay tuned, and go buy iPhone Lounge in the mean time. ;-)