Large search box on front page
The first step is to set "search" as the path of your homepage in the "Site Information" configuration section of the site. This step requires that you have already enabled the search module.
If still have blocks of content on your home page the edit each one of the and make sure to set home page " &lt; front > " as the place where they are not visible.
Add the login block to the footer and you are done.
If the any menu is still showing the create a page-front.tpl.php (D6) or page--front.tpl.php (D7) by duplicating page.tpl.php and the remove the code that shows the menus.
To make the search field larger you can use CSS.