GIMP is an open source Image editing tool. There is a feature to create a slide show in GIMP with the output as Animated GIF format. It can be done in a few mouse clicks. My system is Ubuntu 10.04 with GIMP 2.6.8. Here is the step by step tutorial on this.
Read more here: http://karuppuswamy.com/wordpress/20...-a-few-clicks/