You and your students can create your own animated GIFs by simply uploading a series of images to Gickr or EZGifMaker. See some student examples here. We used Pixie for the artwork, but you could use StoryboardThat or ABCYa! Paint.
We used to love ABCYa! Talkify and Blabberize for creating "talking head" animations, but recently they've been having some problems. You still might want to try them out.