You can use multiple web-based applications out there that can edit images in many ways and some of them usually become a great alternative to our desktop editing softwares. But when it comes to animated GIF support, the list becomes very small and achieving animated GIFs is quite hard without desktop support.
MotherEffingAnimatedGIF is a cool and yet simple web application that can help you quickly create animated GIF images. The application has support for drag & drop and you can add up to unlimited images, you can re-order them and set the result image size and quality. You can also set up the delay between image frames.
After uploading your images, you can preview the animated GIF and download it if it suits your needs.