Show login form in the admin bar for non-logged-in users.
By default, when a visitor accesses your site, the admin bar is not shown. This makes sense for a blog, where you're the only one that has an account.
However, if you're running a site where most visitors need to be logged in before doing anything useful, you probably want to make it as easy as possible for them to log in or register.
This is what this plugin is for: it shows the login form right there in the admin bar, so that users don't need to load another page just to enter their username and password.