As is Sonyimagestation.com Your fingers literally do the very simple walking. You can't save .gif animations on it, though.
The only trick (usually) is the edit work on the image to make it fit in the post frame width. It usually requires a different way of taking images if you don't have the moxie to rotate and crop. Some hosting sites have size limits ..and if your camera doesn't have resolution options, you're taking a big image (further back) and then cropping it very small and enlarging it. Gotta love high megapixel cameras. They can make the smallest image a big file.