You can use iWork Keynote to make video presentations for many uses. You can simply narrate a slideshow, or present a series of points to form an idea. It is a great way to create video without having to appear on camera.
You can use Keynote to create animated charts and graphs. Then, you can export them to use in iMovie and other software to make video presentations.
You can use Smart Builds in Keynote to quickly add a slideshow of photos into your presentation. The photos all exist on one slide, so you don't need to create a separate slide for each image. You can set the transition and other options.
Take a look at 10 different ways you can turn a set of images into a quick slideshow on your Mac.
Gary Rosenzweig looks at how to use iWork's Keynote program to make animated titles for use in iMovie. You can use the transitions and special effects in Keynote to build an opening sequence, and then export it as a video to import into iMovie.