Twitter is a free social networking and micro-blogging service that allows its users to send and read other users’ updates (otherwise known as tweets), which are text-based posts of up to 140 characters in length. As of July 2008, over 2,200,000 accounts were registered.

Twitter in Plain English

Desktop Clients

Twhirl – Desktop client for social software such as Twitter, Friendfeed, identi.ca, or seismic, based on the Adobe AIR platform.

Twitteroo – Windows Desktop client, with several advanced features, that enables you to post to Twitter from the desktop.

Twitterific – Mac desktop client, minimal but beautifully designed and not without options.

Twitterlicious – Windows application that makes using Twitter easier.

TwitterPost – Simplistic Mac desktop client for updating Twitter, coming from Apple.

Teletwitter – Open source twitter client for Windows, with the simplicity and beauty of it’s web 2.0 namesake.

Chirrup – Twitter client with Japanese language support.

Twitter for Vim – Publish tweets right within Vim.

MadTwitter – It’s inspired in Twitterrific, Windows application that lets you read “twits” written by your friends and publish your own.

Twitter CLI – Post tweets via the command line.

What’s Up? – Gadget pulls the data from Twitter every few seconds and streams on to your desktop.

Twadget – Simple gadget that lets you view and submit tweets right from Vista’s Sidebar.

Twitux – Twitter client for the GNOME desktop.

Pwytter – Free Twitter for Windows, Mac, Linux with Asian character support.

KipFolio Widget – Simple Twitter widget for KipFolio.

Twitter-Sync for Yahoo – Syncs Twitter status with Yahoo Messenger status.

TwitterYM – Simple Yahoo Messenger status updater.

Twessenger – Twitter add-in for Windows Live Messenger, automatically updates your Messenger Personal Message at regular intervals to reflect your latest Twitter tweet.

Twit4Live – Automatically notifies you with the latest twitters from your friends, and can one friend can have their Twitters be automatically placed in your Personal Message.

Tweeter – Java desktop client for Twitter.

Mobile

Hahlo – Twitter client for iPhone.

iTweet – Twitter on the iPhone or the Web!

Jargong – IM client for smartphones with Twitter support.

Twapper – WAP based interface for Twitter.

Twitter Flashlite – Mobile application that lets you post to Twitter from your cellphone.

WildSets – Update your friends over the mobile – without having to send an SMS.

TwitterBerry – Twitter built for BlackBerry mobiles, so you don’t need to use SMS.

Search

Twubble – Help to expand your Twitter bubble – it searches your friend graph and picks out people who you may like to follow.

Twitterverse – Search through archived public timelines and tweets.

TwitterSearch – Search Twitter and tweets by word.

TweetScan – Real-time Twitter search.

TwitterLocal – Want to know the locations with the most tweets? Lets you generate an RSS or XML Feed to filter out Tweets around a certain area.

Twellow – Twitter search directory, connect with people.

TwitDir – Allows user to search for users by name, location, or username.

Mashups

GeoTwitter – Twitter Google Maps mashup. It updates every minute and maps anybody in the public timeline who have set their location.

Swotter – ‘reads books’ to Twitter, you can listen to Swotter via the web, via IM, or via SMS messenger on your mobile phone.

Twitter Atlas – yet another Twitter/Live Maps mashup. It looks very sleek and it has a window with tweet history, which is a very useful feature.

TwitterVision – A real-time geographic visualization of posts to Twitter.

TwitterEarth – similar to Twittervision, but based on Live Maps, and works in 3D, too.

Twitterer – a Twitter/Second Life mashups, which shows updates from a certain Twitter accounts over Second Life spheres.

TwitterMaps another Twitter/Google Maps mashup, find up where a Twitter user is located. You can also update your current location with a special command sent to Twitter.

Tools

TweetBurner – Track links you share on Twitter, and Friendfeed too!

TweetStats – Graph your Twitter Stats.

Mail2Twitter – Free service that allows you to post tweets through e-mail, and as well as from any email-enabled mobile device.

TwitterCounter – Add a daily updating TwitterCounter to your blog so everybody can see how popular you are.

TwitterBuzz – It displays a list of most popular links on Twitter. You can see all the Twitter messages mentioning the link.

TwitterFeed – Feed your blog to twitter, post RSS to twitter.

Twitterholic – Keeps a top list of users based on how often the post, how many friends they have, and other factors.

Twittermeter – Twitter meter let’s you query an index of all the words that have been sent to twitter’s public timeline.

Twitteromatic – Tool that posts all sorts of information (weather, Firefox updates) to Twitter automatically.

Twit This – Similar to the popular “Digg This” badges, easy way for people to send Twitter messages about your blog post or website. It’s available as a js snippet, a bookmarklet or a Wordpress plugin.

StockTwits – Twitter for financial investors.

Plugins

Post To Twitter – Firefox search plugin,
post updates to Twitter right from your Firefox Search Bar!

Tweetbar – Firefox sidebar for easy Twitter updating. Works in Flock, too.

Twitterbar – A Firefox plugin that lets you post Twitter tweets from the Firefox address bar.

TwitBin – Send and receive messages to all your fellow twitterholics, right from your firefox browser.

TwittyTunes – FoxyTunes companion Firefox extension – it allows you to post your currently playing songs to Twitter with a click.

Twippera – Twitter widget for Opera that can send and view tweets.

TwitterFox – TwitterFox is a Firefox extension that notifies you of your friends’ tweets of Twitter. (previously known as TwitterNotifier).

Twitter Netvibes module – Netvibes module that lets you update your status at Twitter directly from your Netvibes homepage.

TwitTwoo – Simple little plugin that will allow you to update your Twitter status right from your blog’s sidebar.

If you know of any Twitter related tools, plugins or mashups not included on this list, please let us know, as your comments.