Tools  -- 

Here are the 3 most critical tools to use when playing poker

  1. Pokertracker -- Awesome tracking software.  lets you track your wins and losses, evaluate your own play, evaluate other's play, playback hands easily.

           a) An overview of why I think Pokertracker rocks the house

            b) Some key metrics in Pokertracker 

            c) Analyzing your Own Play in Pokertracker

            d) Differences in Play by Limit from Pokertracker

  2. PokerAceSoftware -- takes pokertracker data and transposes it directly onto your tables while playing.  You get tons of updated data on how your opponents play.

  3.  Twodimes -- plug in your hand, your opponents and any part of the board to understand how much equity you have in a given situation.

And one to use when not playing poker: the 2+2 Strategy Forums

But there are a host of other critical information sources to help you out