Pixel Art Studio - A purpose-built drawing tool for pixel artists
CSS Sprite Generator - A tool for generating image sprites and CSS for your web site.
Aseprite - Aseprite is an art program dedicated to the creation of pixel art.
Sprite Cow - Sprite Cow helps you get the background-position, width and height of sprites within a spritesheet...
Pixel Art to CSS - Draw and animate pixel art, export the results to CSS
SpritePad - The easiest way to create your CSS sprites