Nukescripts.net (NSN) has just such a block in use on the right hand column of thier site. A Quick search of thier downloads section brought me to
this block
Not sure if that is exactly it or not as I am at work and haven't had time to download and test it on any of my sites, but a quick scan of the .php file included looks as if it has login functions so I believe this is it.
However, personally I think you are really asking for trouble by putting a box on your front page saying admin login here. Why tempt people to start trying login and password combos. Just doesn't take all that much effort to type admin.php after the URL. And sure every good nuker knows how to get there but at least it isn't just in plain site where it could tempt your bored would-be hacker type

Now that I think about it I wonder what it would effect if I renamed my admin.php to something else just to further increase security.
Anyways I digress, if that is what ya want there it is, just make sure you have a strong password (ie at least 8 characters alpha-numeric with upper and lower case)
