Creating animated cartoons sounds a bit daunting, but if you start by creating doodle stick animations with Stykz, it's a different story.
Stykz is a dead easy animation tool with which you can create basic animated sequences with stick figures and other geometrical shapes. You can't use your own drawings or add a background, but on the upside Stykz offers you complete control over each single frame, and a dozen points in each figure to create movement.
Each new frame you insert in the animation sequence shows an outline of the previous position so that you can create the new movement with higher accuracy. The program also includes a built-in player to preview the final animation.
Stykz lets you export your animation to several different formats (animated GIF and QuickTime movie among others) but has one main drawback: the Undo tool doesn't work. The author has promised that it'll be fixed in future releases though. Meanwhile, you can save at different stages along your work and revert the animation at a previously saved point as a workaround.
With Stykz you can learn and practice the basics of animations by creating basic animated sequences with simple stick figures.