Picasion is a great online free to use tool, that allows you to instantly generate animated gif files by simply uploading the pictures you want to appear in the resulting animation up to the site. There are a few options you can set to tweak the output (like animation speed and output dimensions for example), but for the most part creating your own animated gif file is as easy as clicking on the upload image button and then pressing the generate key.
In terms of feeding it source images with which to create the animated gif, naturally you can simply upload images directly from your harddrive, though Picasion makes a great little extension on this by also giving you the option to push images directly into it from either your Picasa Web or Flickr accounts.
Outside of the garish littering of adverts all over the site, Picasion really is a nifty little find and will have you spitting out animated gifs faster than what you can blink and quicker than what you would have imagined – all without the help of an expensive graphics software package! :)
Related Link: http://picasion.com/