1. obviously collin moshman-sit n go strategy
2. harrington vol. 1-3 for tournaments, winning poker tournaments one hand at at time by eric lynch, jon van fleet, and jon turner
3. bluefire, and card-runners
4. HEM is a hand tracker tool, that allows you to study your hands and games on the table, and off the table. It allows you to keep stats on your opponents in real time, and allows you to filter your stats in the program by anything you can imagine just about. Lets say you wanna filter by opponent having flush draw on flop when you have top pair, best kicker, you can see all the hands that you have played with that filter. There are obviously too many features of HEM to list here, but it is strongly recomended and a must have for any serious poker player. Great tool for multi-tabling where you can't study all of your opponents.
5. It is a very handy tool, if you are not that good at calculating pot odds
, and the sort, but a better real-time odds calculator is holdem inspector. check it out @ holdeminspector.com.
6. obviously you need to practice alot, and if you are using a tracker make sure you take time to analyze your game off the table as well. Soak up as much information as you can.