Scripts and libraries

Applescript 

• ASTwitterLibrary 1.1 - Integrate Twitter into your Applescripts or Applescript Studio project.
• iTwitStatus is a way to use your Twitter as your iChat Status via QuickSilver.
•  | Tweet - update Twitter via Quicksilver
• TwitterAdium by Jesse Newland
• TwiTunes is an AppleScript for Mac OS X that posts the current iTunes track to Twitter: "Linda is listening to "Take on me" by A-ha." Can be customized easily.
• iQuickTwitter - My Quicksilver + Twitter + iChat + Growl Hack: An AppleScript that integrates Quicksilver, iChat, and Growl with Twitter.
• Growlified Tweet Deluxe (based on Ted Leung's Growlified Tweet) is a Quicksilver AppleScript action that uses Growl and checks message length before posting.
• Qurl for Twitterrific. Applescript to convert URLs to Qurls. By Greg Fischer. More info here (UPDATED. No longer dependent on secondary scripts)

BASH shell 

• Twitter using BASH and cURL on a Mac Terminal line - should work with any OS that supports BASH and cURL
• Parses BBC rss feeds and pipes them to Twitter using cURL - in BASH, by Guillaume Riflet.
• Display Tweets using notification daemon (Gnome, etc) - in BASH, should work in any disto with notify-send.
• Post /w BASH+cURL + Spell Check + Length Check - More stuff on top of the script above.

Jabber 

• Jabber::Simple (src, doc) is a simple (duh!) Ruby library that aims to make the implementation of basic Jabber functionality trivial
• TwitterPated is a script to interact with Twitter via Jabber to make it simpler for multiple people to publish to a Twitter identity.

Java

• twitter4j
• JTwitter is a simple Java interface to Twitter. It provides nice Java methods and objects for accessing Twitter.
• Twitter taglib - access to Twitter right from your JSP (or Coldfusion) pages

JavaScript

• TwitterJS easy to implement JavaScript twitter badge with lots of options to customise appearance.

Perl 

• Perl command line tool for setting twitter status by Shantanu Goel
• Perl command line tool for direct messages by Stephane Kattoor
• wd - a perl script to get/set twitter status from the command line. Source.
• Twitish A twitter shell written in Perl for Linux and *nix.
• How to hook twitter into a IRC channel by Harper Reed
• Email to Twitter by Leonid Mamchenkov
• Updating Twitter from irssi by John Anderson
• Reading and updating Twitter from irssi (with Ping.fm support) by Remco Brink

CPAN Modules 

• Search CPAN for Twitter
• Net::Twitter by Chris Thompson (Debian Package, relies upon libjson-perl)
• Twitter::Shell by Daisuke Maki
• • twitter shell
• POE::Component::Client::Twitter by Kazuhiro Osawa
• • twitter irc gateway

Movable Type 

• MT-Twitter An easy way to announce Movable Type blog posts via Twitter. From Chopstix Media.

PHP 

• Syndicate Twitter to your blog by David Kadavy
• RSS to Twitter by Paul Stamatiou
• MailTwitterPHP is an email to Twitter gateway script that attempts to connect to a specified IMAP inbox, cycle through all email and attempt to post the body of each email as a new Twitter to a specified Twitter account. Requires a PHP install with IMAP support compiled in.
• Twitter + PHP Update your Twitter status from within your PHP scripts
• Twitter2HTML Show your latest tweets on your website with this simple PHP script. (via API, not RSS for instant updates. Requires cURL.)
• TwitterSig Show your latest tweet in an image file for use in forum sigs, etc. Requires PHP5.)
• PHP code from scratch to get the user updates and display it on your page the way you want.
• TwitterOAuth was the first PHP library that supported OAuth, is lightweight, easy to use, and released under a MIT license.

TYPO3 

• timtab_twitter by Frank Nägler aka NeoBlack (announcement)
• fn_lib contains a PHP twitter client by Frank Nägler aka NeoBlack (announcement)

Drupal 

• Twitter Module for Drupal by James Walker aka Walkah (announcement) automatically sends updates when new content is added
• Send Twitters from Drupal - a simple form for sending a twitter message by kaerast
• Twitter Direct Message on new comments in Drupal - get a twitter direct message everytime someone submits a comment baramunchies

Python

• Twitty Twister Twisted Python library with OAuth support by dustin and Kévin Dunglas.
• Tweepy by Joshua Roesslein.

.NET

• OAuthLib Library for OAuth protocol, which can use for Twitter Client program.

Ruby

• Safaritweet - Posts the title and URL of the currently active Safari tab on Twitter, hashtags can be passed in as command line parameters. Uses RubyOSA for AppleScript magic, twitter4r and ShortURL.

Lua

• LuaTwitter - by Kamil Kapron. Simple module for Lua developers. It provides access to the Twitter API methods.

Dreamweaver

Twitter Integration Dreamweaver Toolbar: provides a collection of tools to help you to integrate Twitter services in a website using Dreamweaver. It's provided as a Dreamweaver Extension, and adds a new category to Dreamweaver Insert Bar and to the Insert Menu. You can customize the theme and various display options to match the style of the website, this way providing valuable blocks of content to website's visitors.