Justin Tadlock invites you to join the WordPress theme review team. Any theme submitted to the WordPress.org Theme Directory gets reviewed by this team first, and the deluge of new themes is tough to handle by this small team of twelve.
I am not part of the team, but I’ve taken a look at their process. Being part of the team is without a doubt one of the best way to learn to be a world-class WordPress theme developer. You will learn so much, you begin to notice flaws even in the most popular WordPress themes, and instantly know how to make a better one.