Hashwork lets you attach files, images, and Wiki-style formatted text to your tweets on Twitter.
Twilk.com – A Twitter background generator
A Twitter background generator which will create a custom background made up of your friends’ profile photos.
nom.ms – Tweet pictures of food
Upload and view Tweet pictures of food from restaurants or recipes.
TwitrPix – Upload, share and post photos to Twitter from mobile
TwitrPix – Upload, share and post photos to Twitter from mobile, desktop and email. All photo comments are posted to Twitter as @replies.
ThumbSnap – Share your photos on Twitter
This Share your photos on Twitter. Fast, free, simple and unlimited storage. Sign-in with your Twitter account (using oAuth so no password required) to upload multiple photos in one go and share them on Twitter, Facebook, MySpace, Digg, Reddit and many more.
FolExt – share photos on Twitter
lets you share photos on Twitter. You can post pictures to FolExt from your phone, our API, or through the site itself.
Tweetmondo – Share your location
This allowes you to share your location and meet people nearby in real time.
Localtweeps – find Tweeps in your city
Localtweeps was created to help localize the Twittersphere. Get found and find Tweeps in your city and zipcode.
ChirpCity – Twitter by city
This is Twitter by city. Local search, latest tweets about and from your city and a top users list.
Breaking San Francisco News
One of many Breaking News city sites that aggregate the best Twitter feeds in a city by category: news, events, shopping, food, etc. Los Angeles, NYC, Boston, London, Toronto. See one of the sites for a list of all cities. Click here to visit Breaking San Francisco News
Tupalo.com
Find, rate, review and Tweet about the best local businesses in your neighborhood or around the World.
twitRobot – upside down twitter messages
Freak your friends using upside down twitter messages like this “sʇǝǝʍʇ pǝdılɟ“.
Twitdom – A comprehensive database of Twitter Applications
It is a comprehensive database of Twitter Applications with thousands of apps categorized, tagged, and ranked.
Twi5 – A one stop shop
It is a one stop shop for finding cool twitter applications.