Kdenlive is an acronym for KDE Non-Linear Video Editor. It is primarily aimed at the GNU/Linux platform but also works on BSD and MacOS. It is currently being ported to Windows as a GSOC project.
Non-linear video editing is much more powerful than beginners’ (linear) editors, hence it requires a bit more organization before starting. However, it is not reserved to specialists and can be used for small personal projects.
kdenlive