Aseprite - Aseprite is an art program dedicated to the creation of pixel art.

Lospec Pixel Editor - Free online pixel art program. It's easy to use, intuitive and unobtrusive.

Pixel Studio - The Pixel Art Is Always Fun

Grafx2 - GrafX2 is a bitmap paint program inspired by the Amiga programs Deluxe Paint and Brilliance.

Piskel - Piskel is a website where designers online create sprites or pixel art.

Pixel Art to CSS - Draw and animate pixel art, export the results to CSS