catfish (A versatile file searching tool)

Catfish is a frontend for different search engines (daemons). The
interface is intentionally lightweight and simple, using only GTK+ 2. You
can configure it to your needs by using several command line options.

Supported backends:

find, (s)locate, doodle, tracker, beagle, strigi and pinot

NB: Catfish can be integrated into Thunar as a search option. A small howto
can be found here:

http://www.dawoodfall.net/index.php/8-pages/news/35-integrating-catfish-into-thunar