This will shorten the link you give it with is.gd then send you on to Twitter, with the short link pre-filled in the tweet box.
I don't get to know who you are on Twitter, and all the authentication happens on their secure servers.
You can use this to tweet links from any modern browser by adding this bookmarklet to your bookmarks: (dragging the link below to the bookmarks ought to work, or copy the text underneath)
window.location='http://ashok.org.uk/hacks/linktweet/?link='+escape(window.location)Notably, this works on the iPhone, which had no copy & paste when I wrote this; the simplest way to do this is to add it to your desktop browser then sync your bookmarks using iTunes.
Inspired by the Twitterlink app. I just wanted to avoid using an app, especially one which wants your Twitter credentials.