I use bit.ly and I also use Chrome for browsing, and these two work hand in hand with instant short url’s using the bit.ly extension for Chrome.
There is also a bit.ly extension for Firefox, but I’ve tried installing it twice and it never worked. But then again, I use other browsers these days just to check cross-browser compatibility of the websites that I make, so having bit.ly work in Firefox is the least of my worries.
The bit.ly extension for Chrome adds a tiny icon right beside the the Customize and Control wrench on the top right corner of the browser screen. When you have the page that you want to tweet or share in any social networking site, just click on the tiny yellow fish and a small pop up will appear just below it, with the current page’s title and shorted URL.
The link is also automatically copied (depending on your settings) to the clipboard, so all you have to do in twitter, or wherever you want to share the link, is paste the short URL.
Sure beats going back and forth on tabs between my pages and tinyurl.com …