I discovered this app "Seam Carving GUI" - what a name! This is an open source, all platforms software to manipulate your photos based on the CAIR library (CAIR stands for Content Aware Image Resizing). This is simply amazing stuff! You can resize images (stretched,...) and remove elements of your photo (you know, the guy in the background of your beautiful photo).
To this (remove small fish and stretched):
This is the kind of app that can really change a photo from good to best.