GOLIBRARY
This site is a collection of resources for the study and reference for the game of go. It does not aim to introduce the game or teach the rules -- as there are plenty of places on the internet that do these things very adequately.
Most of what can be found here is probably useful for single-digit kyu to low dan players. If you're a beginner your time is probably much better spent simply playing (or solving problems) rather than going through difficult and technical variations.
While there is no substitute to playing, when it comes to getting stronger reviewing your own games and studying those of other players (preferably stronger than you) is an extremely useful way to learn. In order to do that, it is helpful to mentally break up the game into smaller, manageable constituent parts and approach those in isolation. On the largest possible scale, this would mean divisions between opening (fuseki), middle game (chuban) and end-game (yose). Those parts can be further taken apart: fuseki can be analyzed as a whole-board combination of different joseki and extensions along sides. Whenever there's a close engagement, be it in opening, middle or late stages of the game, it becomes (or at least threatens to become) a tsumego problem. Fights, when they do erupt, can become quickly very complex, so it is a good idea to be familiar with standard situations and sequences. Although rote memorization is seldom ultimately useful in go, knowing the standard shapes and lines of play give a baseline from where to start reading out the situation and provide inspiration when faced with a difficult choice.
On this site, you will find a joseki database, a number of fuseki dictionaries for some of the most common openings (along with countermeasures and often with illustrations of practical application in professional games). There are also several hamete (trick play) variations, along with refutations, for most common corner opening patterns such as hoshi, komoku and takamoku, as well as a collection of commented pro games. Taken together, those should be a useful set of tools for studying general concepts, learning standard sequences, generating new ideas and finally, reviewing your own games.
