SpritePad is described as 'Optimized for speed: No download, no setup, no long-winded uploads. SpritePad works hassle-free directly in your browser, just drag & drop your images and you can immediately work with them to create your unique CSS sprites' and is an website in the Development category. There are five alternatives to SpritePad, not only websites but also apps for Windows. The best alternative is Sprite Cow, which is free. Other great sites and apps similar to SpritePad are CSS Sprite Generator (Free, Open Source), SpriteSheep (Freemium), Spritesheet (Free) and CSS Sprite Generator (Beta) (Free).
SpriteSheep lets you easily and visually generate CSS sprite sheets and CSS code with all sprites positions offline. CSS sprites technique helps to reduce HTTP requests and it's much easier to use CSS class instead of proving URL for each image.