A list of browser plugins and extensions enabling users to send and receive tweets directly from their Firefox, IE, Chrome, Safari, Thunderbird, Opera, etc web browsers.

Services that enable users to view tweets and all of the replies as a threaded conversation.

Third party software applications that enable users to send and receive tweets from their PC or Mac computers

A list of applications that enable mobile devices to send and receive tweets from Twitter

Twitter services that provide visibility into hot topics, popular people and the websites that people are tweeting about.