ImageMagick is a collection of command line tools which allows you to do lots of cool things with images. I use it a lot to create animations, in particular to add multiple images and text to a single slide. If you want to make something simpler than a movie, it is possible to generate a gif animation using ImageMagick. The simplest command is:
convert -delay 100 *files.png animation.gif
Which will create an animation from all files matching ‘*files.png’ with a 100 x 1/100 s (1 s) delay between images.
If you want to add a title for each image you can also do this with ImageMagick, using something similar to:
convert image.png -gravity south \ -strokewidth 10 -pointsize 100 \ -fill white -annotate 0 "Title" \ image_with_title.png
An example script, using RSGISLib to colour images and imagemagick to create a GIF, is available on github.