I think your Advanced Search Widget is the exact type of functionality and simplicity my site needs. But I would like the search to be horizontal across the page, instead of vertical in the sidebar. Is this possible?
The widget plugin provides a PHP snippet by which you can insert in a page or page template to show the form anywhere.
Also, the plugin doesn't provide any layout on its own. It uses the default search template search.php in your theme and display results. So, if you customise your search.php that way, so you can achieve what you want.