Gloobus is a sexy file previewer for your Gnome desktop
In other words, you can access a huge number of file types without first launching the applications associated with that file first. It's useful for browsing your pictures (from, say, last night pub) or to create a simple slide show on your desktop.
Gloobus can currently preview over 40 file formats including image, document, audio, video, and programming language files.
Ubuntu and all Debian based distributions can get Gloobus installed by downloading the .deb file, Archlinux users can download their package here. For any other Linux distribution you can compile Gloobus from the source code.