I have accounts in close to 10 Stack Exchange powered sites. I want to change my nickname in all the sites. Is there a way I can do it from one page that would reflect in all of the Stack Overflow/Stack Exchange sites ?
This changed recently. There's a tab at the top of your profile:
This links to https://stackoverflow.com/users/edit/current.
To save to all the sites, click the "Save and copy changes to all Stack Exchange communities" button at the bottom: