This bookmarklet will transform all the available links to sign up links after searching for a username on usernamecheck.com. Currently you search for a username and see whether that username is taken over a number of sites, and when it's not they link to the site; but you really want a link to the sign up page. After clicking this bookmarklet all these links will be transformed. Install it.
To install drag this link to your toolbar...
and then after entering a username at usernamecheck.com, click this link and all the available links that point to the home page will transform into sign up links linking to the registration pages.
The next step is clearly to show if you are the taken names...but I won't take those steps.