DoesFollow

DoesFollow offers an easy way to find out if someone follows you. To use the site, enter in your Twitter username and theirs and click "check." The site will return a "yup" or "nope."

Twitter Ratio

The site at Twitter Ratio help you measure your ratio of your followers to friends and determine what that means. The higher the ratio, "the more Twitter heat you pack." According to the site:

• A ratio of less than 1.0 indicates that you are seeking knowledge (and Twitter Friends), but not getting much Twitter Love in return.
• A ratio of around 1.0 means you are respected among your peers. Either that or you follow your Mom and she follows you.
• A ratio of 2.0 or above shows that you are a popular person and people want to hear what you have to say. You might be a thought leader in your community.
• A TFF Ratio 10 or higher indicates that you’re either a Rock Star in your field or you are an elitist and you cannot be bothered by Twitter’s mindless chatter. You like to hear yourself talk. Luckily others like to hear you talk, too. You may be an ass.

Pick of the Twitter

The site at pickofthetwitter.com aims to find the best tweets out there and highlight them. Tweets are pulled off of the public timeline using some secret-sauce algorithm at a rate of one tweet per hour, 24×7x365.

Tweeq

Tweeq is an application that lets you find out which cliques ("tweeqs") you are a part of on Twitter. The app crawls through your following/followers lists to find out who you friends are and how you all are grouped together. To use the app, enter in your Twitter username and then it will venture, in their own words, “in ur tweets, revealin’ ur largest cliques.”

Custom Twitter Groups

Christoper S. Penn shows you how to make custom Twitter groups using Yahoo Pipes. Check out his blog post for the details.

FAVRD - List of Favorite Tweets

FAVRD lists interesting things that show up on Twitter, based on the number of times an item has been declared a ‘favorite’. And by interesting they mean funny, weird, unique, or random, apparently. Items are voted on to determine which ones are the most favorite. You can sign up to vote by entering your credentials on the about page.

Picobuzz

Picobuzz is a site that lets you track the buzz on Twitter. This site tracks the mentions of popular words (like "iphone" or "wii") and then displays them in a Top 20 chart. Picobuzz is updated every day and you can view today’s buzz and yesterday’s buzz, but no other historical data. Next to each buzzword are five avatars of the twitterers who tweeted it last with a link to "more," which will then display the other avatars of those who tweeted the word.

TweetCube

TweetCube is a free file sharing service for Twitter. You can upload as many images, archives, videos and songs as you want and share them on Twitter with your followers. The maximum file size you can upload is currently 10 MB. Old files are deleted after 30 days.

Twitter Clients for Linux Users

The Linux and Open Source blog posted a list of Twitter desktop clients which includes:

• ktwitter - A simple Twitter script for KDE.
• twitter.el - Twitter from Emacs
• twit.el - Another Emacs client.
• Vim Twitter - Twitter from Vim
• gTwitter - a Twitter client for Linux.
• GtkTwitter - a Twitter client for Linux and Windows which using GTK.
• Twitbar - a Twitter client for Gnome users to post from the Deskbar
• Twit and Wayd - Two addons for Gnome Deskbar that allow posting updates to Twitter
• BLT - twitter meets the Bourne shell, with a hint of biff.
• Twitux - a Twitter client for the Gnome desktop. Features includes: gui-notifications, url tinyzer, and more..
• ZenTwitter - bash script which uses zenity and curl (could be launched from custom desktop/menu/panel icons)
• mitter - A very simple Python and pygtk client.
• prism-twitter - prism based

(List Via)

Twittai

Twittai is a Java mobile application designed for Twitter. The app lets you view your archive, replies, inbox favorites, friends, and followers. You can tweets, read your friends’ timelines, find and follow people, and view profiles. Twittai is compatible with more than 200 phones and Windows mobile with CLDC 1.0/MIDP 2.0. Supported phones include Nokia, Motorola, Sony Ericsson, Samsung, HTC, etc. To download, point your phone’s wap browser to http://m.twittai.com and click Download.