Various programs which help you in studying the game of go.
A go database program, including pattern search and search for game properties. Open-source, runs on Windows, Linux and Macintosh OS X.
Drago is an SGF viewer/editor which you can also use to work through problems (like uliGo) and to play against GnuGo. Windows. Freeware.
GoGrinder is a Java program for practicing go problems. It uses problems in SGF format. 347 problems are included in the install, and thousands more are easily downloadable (pointers in the documentation).
Written by Anders Kierulf. Commercial (there is a free demo version). Windows.
Online pattern search in a database of around 70,000 games.
A go database program. Open Source, Linux/Windows/Macintosh.
An sgf editor and IGS client for the Mac.
An Android app for studying go (tsumego, database of games, ...). Commercial (7.99 EUR + In-App purchases at the time of this writing).
A go database program, with a pattern search engine, and (in the full version) a huge amount of games: more than 700,000 pro and top ama games. They also have a joseki database, and OCR software for go diagrams.
This is a program to practice solving go problems. It reads problems in SGF format, and rotates/mirrors them randomly so that in order to answer you really have to know a particular shape, not just one particular position. Free. Linux/Windows/Mac OS X.