TweetDuck

TweetDuck: Easily manage multiple Twitter accounts with this small, open-source application

TweetDuck is an intuitive desktop Twitter client that lets you easily manage multiple Twitter accounts, sort their contents and schedule tweets.

The app’s interface can be customized using the two built-in themes, but you can also change the column and font size, as well as avatar shape.

The contents of your Twitter accounts can be sorted into multiple columns for post tweets, mentions, collections, notifications and so on.

Furthermore, TweetDuck can send desktop and sound notifications which you can customize to your liking.