Upload & Sell: On
I like the small free ones better myself. But either way the process is the same. Process your images as you normally would and use the GIF tools to set the kind of dithering, transparency, speed and looping you want and save it out. Pretty simple. If you already have PS then sure go for that... But keep in mind PS doesn't allow bi-directional looping (ping-pong), nor offer useful controls over dynamic pallets and transparency like many of the free or share ware ones do.