Yesterday Facebook announced that they were going to make it easier on Pages to change their username/URLs. I know this will help out a lot of people. You still cannot change your Page name (unless you have less than 200 fans) but username/URL is a good start.
To change your username: go to your page > Edit Page > Update Info > Change Username.
For more information about Facebook Usernames, you can check out their help center section for it.