Sprite Cow is another one which is open source and works very effective by auto-recognizing the different elements inside a single image.
So, you design the sprite image in your favorite imaged editing application, upload it to Sprite Cow and simply click (or click + drag) on each element to get their width
, height
and background-position
as a CSS rule.
Website: http://www.spritecow.com/
Download: https://github.com/jakearchibald/sprite-cow