From The Mana World
When I started with pixel art: 
and after 3 years practice: 
So don't give up, and practice, even when your work sucks :)
- So You Want To Be A Pixel Artist by Tsugumo. (more recent version [1])
- Mark's Pixel Art Tutorial
- Derek Yu's Pixel Art Tutorial
- Pixel-Zone Tutorials
- Pixel Art Links
- Mruk's Desert Well Tutorial
