How about a Search Box for the frontpage?
 

Has this been done already?

A simple textbox 'quicksearch' of all categories with no price range or field options at all. You could have a simple link underneath it to the 'advanced' search at mysite/search.php

It includes a real basic one you can use but it doesn't include the categories.

Just use this:

Very cool, I wouldn't underestimate a good, basic function like this. For the end user it is very important.