Extension: Search Filter

Hi there,

I was wondering if anyone knew of an extension that would add a filter to the search page?

For example, if you go onto this site: http://www.allendisplay.com/ and type in something into the search, when it has results, it will also add filters to narrow down the search as well.

Any help would be appreciated. Thanks!

you can look at this

http://www.opencart.com/index.php?route ... on_id=4596