ERIMANew: Astral Fish - tiny songs for your phone.

Go problems (tsumego) collected in PDF format. They range from beginner to advanced and contain no answers, only problems.

Check out this introduction to the Igo Hatsuyo–ron collection:

This problem collection was compiled around 1710 by Inoue Dosetsu Inseki, fourth head of the Inoue house and fifth Meijin Godokoro. It was designed for training of the best students of the Inoue school and was kept secret for a long time.

Igo Hatsuyo-ron consists of 183 mostly insanely difficult problems and is aimed at serious players with deep interest in the game. While solving the problems takes many months, possibly even years, finding the solution is always particularly rewarding.

Totally badass.