DigiKam is an advanced digital photo management program designed to import, organize, enhance, search and export your digital images to and from your computer. This is an open source and cross-platform program, and the default photo management program on KDE.

More about DigiKam, refer to its homepage: http://www.digikam.org/drupal/

DigiKam is by default available in Ubuntu Software Center, but it might be old. To get the most latest version, add this PPA:

sudo apt-add-repository ppa:philip5/extra
sudo apt-get update
sudo apt-get install digikam 

Launch digiKam from Applications -> Graphics menu.