SpriteSheep is described as 'lets you easily and visually generate CSS sprite sheets and CSS code with all sprites positions offline' and is an app in the Development category. There are five alternatives to SpriteSheep for Online / Web-based and Windows. The best alternative is Sprite Cow, which is free. Other great apps like SpriteSheep are CSS Sprite Generator (Free, Open Source), SpritePad (Free), Spritesheet (Free) and CSS Sprite Generator (Beta) (Free).
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.