sushi is a quick previewer for nautilus

 Sushi is a GtkClutter and Javascript-based quick previewer
 for Nautilus, the GNOME desktop file manager.
 Sushi is a DBus-activated service. It is capable of previewing
 documents, PDFs, sound and video files (using Gstreamer),
 some text files, and possibly others in the future.
 .
 To activate the preview, left-click the file and hit space.
 The preview can be closed by hitting space again, or escape.