Blender has a built-in video editor. Learn how to work with it and create a cool short videoclip.

An often underestimated function of Blender is the Sequence Editor. It is a complete video editing system that allows you to combine multiple video channels and add effects to them. Even though it has a limited number of operations, you can use these to create powerful video edits (especially when you combine it with the animation power of Blender!) And, furthermore, it is extensible via a Plugin system quite alike the Texture plugins.