This plugin allows blog user to change their blog URL from existing one (subject to availability). The admin page can be access at Option->Publishing. This plugin simply modify 4 fields, three fields in user blog option table and one in the wp_blog table. When user enter a new blog address, the plugin will check for rule that apply when one sign up for a new blog. So yeah, blog must have at least 4 characters, blog names may not contain the character "_", etc. Let me know if you have any questions or comments. Here is a screen shot. Note: If you download the earlier version, you will need to change domain URL to your domain manually, or simplify replace it with the current one. Note:If you are using multiple domain, you will need to hack it to make the domain switchable. Right now, it will just use the domain with site_id = 1. Intall: Upload and place it in your mu-plugins folder. That's it.