For those of you who have a Twitch account, Twitch has reset a bunch of inactive usernames yesterday if you are interested. You can't create a new account and register a username that has been released, you need to have an account that is at least one month old. You then have to go to your account settings on Twitch and if you haven't changed your username in the last 6 months, it will allow you to change your username.
So if you've wanted a particular username but noticed that it was on an old inactive account, it may have been reset since yesterday. Again though, you can't create a new account and then try to change your username or directly sign up under one of these re-released usernames.
Perhaps your favorite sports team is now available, a word or name you like, match it up with your gamertag or NT username, ...