Are you referring to your username link? You can change the link manually as frequently as you like to another blog you have registered under the same username. That’s the only method I know of. Dashboard -> Users -> Personal Settings -> then scroll down to ‘Account Details’. In the spot where it says ‘website’ type the URL for the blog you want and save the changes. Now… when you comment here and on other blogs, your name will link to the blog you chose.