A collection of over 1000 problems, including the famous Korean Problem Academy and Ancient Wei-qi Patterns.
Over 9000 problems. A good variety of problems, in an interactive format. You can have the solution with the solution shown in several formats. Anyone can add new problems to the site.
Two new problems each week by top Japanese amateur Minoru Harada, answers the following week. Over 500 problems so far. The site has seperate Japanese and English language sections.
Each of these pages leads to 20 life and death problems.
Various problems and sets of problems. In particular, see:
A new problem every month since January 1996 until December 2005.