http://h34nug3iwqjf2376fmmzdhgqivckzemcujmarlptfqeqtq7vya47yyad.onion/2007/02/28/digikam-advanced-photo-management/index.html
This makes a big difference when trying to find and organise your photos as opposed to the simple date order of some programs. Once in the main window, a left click opens the photo in the digiKam Image Editor. Right click for more options, including opening the photo in other editing programs (such as the Gimp).