Lots of Twitter profiles now feature icons supporting social and charity causes. Twibbon is a cool service which will let you overlay icons of your choice on your Twitter profile for free.
Twibbon is now the easiest way to promote awareness of your cause on twitter, by overlaying a support icon over your Twitter profile. There are hundreds of causes to support and there is surely one you are passionate about. Just click on the cause you like, it will make you login via Twitter (which is safe), and your profile is changed. You can also revert back to your original profile by selecting your original icon from your unique profile page (like mine).
I also created a new Twibbon and it adds an Indian flag to your Twitter profile photo