With this plugin you can use customize the appearance of the WordPress login page and dashboard.
There are already quite a few plugins that offer similar functionality, but the fact that my plugin uses the WordPress Media Library makes it super easy to upload and edit your own logo.
I also am not aware of any other plugins that allow you to specify a clickthrough url for the logo.
Finally, this plugin is ready to be localized. All you have to do is to use the POT file for translating.