Beagle: the desktop search engine for linux
Since Google desktop is still not existing for #Linux, You can also try to use Beagle:
" Beagle is a search tool that ransacks your personal information space to find whatever you’re looking for. Beagle can search in many different domains."
Beagle is supporting the following filetypes, and has a nice interface which also act like a previewer of all files found. Installed as default under Suse 9.3 and originally developed for Gnome desktop, it is running perfectly in KDE.
The latest version is now indexing not only Your HOME directory but also all disks. Acuracy is quite good, and the interface is responsive enough. Written in .NET framework but running under Mono, it is a brillant demonstration of what open source has to give.