Natron

Natron is a digital compositor for VFX and motion graphics. The node based engine suits my background in software engineering.

Natron can be used to perform colour correction and a host of different visual effects on your photographs.

Whether you expect to be performing any Visual FX or not, it is worth looking at a few Natron tutorials as they'll give you some background into some of the basics for animation and editing. Open Visual FX is a good source of information and the Compositing in Natron video tutorial is a great place to start.

Tip: Natron can be quite overwhelming to the beginner. The merge node will feature in your graphs - the main image/source should be connected to the B (base) input and the images/sources to merge in should be connect to the A inputs.