Want to check whether your name is still available at social networking and Web 2.0 sites? Just visit http://usernamecheck.com/, key in your name and click the ? button.
According to the site, ‘sridhar’ is available at Digg when it’s not. So YMMV.
It’s a good idea to go ahead and register at those sites (that you think might be worth creating an account at) where your desired username is still not taken up.
By the way, does anyone know if TinyURL allows user registrations?