Creation of png:
I use spritepad to create the png image, just drag and drop your images to create the sprite: http://spritepad.wearekiss.com/ (but as I assume you dont want this step).
CSS:
After this I import the image to spritecow and get the css for every image (double click every image to get its height-width and coordinates): http://www.spritecow.com/
You could use spritepad only but I prefer to use it only for the creation of the sprite. For css, spritecow seems easier to me. Anyway its up to you.