[belladoggy]

You might be able to use pixlr.com, but I'm not sure if it has that ability yet. Pixlr is essentially a free online version of something similar to photoshop; I believe you would use the "select by color" or "wand" tools; make sure the lock icon on your image/layer is changed to a check mark (you can do this by clicking on it), and go to the "edit" menu at the top and select "clear". You should see a grey checkered background which will show you that you have transparency. I don't think it supports animation yet, though. You can add layers, but it won't open .gifs as layers.