A great tool for analyzing poker play. Poker Tracker imports hand histories (yours and others') into a database. It then gives you statistical views on that data which can help you find your trouble hands, as well as understand the statistical realities of play. It is highly recommended.
Many people use Poker Tracker to analyze their own play. Many people spend a lot of time FindingLeaks.
Many people collect hands which are observed (they didn't play.) They then use the database as a source of information on those players while playing. Some people even use the data to identify bad players to look for on tables.
Many people online erroneously refer to this sort of data collection as data mining, which is wrong. Data mining refers to going through the data after you've collected it, looking for information. In a sense, you are mining for information in the data.
Poker Tracker Forum member Vern put a lot of time into developing a great graphing tool to work with Poker Tracker called PokerGrapher. He has released the project into open source and it is hosted here.
Future pages
Common Poker Tracker explanations (fields defined)
Commonly asked questions
Need a new, empty HHDB?
For PT Hold'em: http://www.pokertracker.com/hhdb.mdb
For PT Omaha: http://www.pokertracker.com/hhdbo.mdb
For PT Stud: http://www.pokertracker.com/hhdbs.mdb
Common procedures (setting up for multi-computer, setting up Postgress)
PT add-ons: HUDs
PT add-ons: Graphers
Postgress-specific stuff (queries, etc)