The worlds largest poker training site and by many regarded as the best.
A video community for poker players
Poker players who are serious about online play really needs to have a tracker that keeps track of their own and their opponents play.
A tracker can show how many hands you have played against an opponent, how many hands they play, how often they raise, how aggressive they are and much more.
There are several alternatives, personally I use Holdem Manager
(I have tried Poker Office and Pokertracker as well).
The worlds leading poker tracking software.
Odds and equity calculators
You have put your opponent on AA-77, AK, AQ preflop and you have JJ. The board comes with low cards with two of your suit and your opponent goes all-in.
What is you equity in this hand - at what odds would a call be profitable? This is an example of a situation where a tool like Pokerstove can help you with the analysis.
Pokerstove is free and it is my prefered choice, but there are many alternatives.
Poker room reviews
Best online poker rooms
Find the best online poker rooms. PlayersJet has reviewed, rated and ranked 900 plus online gambling sites to help you practice safe bets.
Free Poker Tools, Poker Like a Pro...
A collection of free poker tools.
Two Plus Two
Book publisher and great poker forum, probably the most active there is. If you have a question that you think might have been asked before a great place to start is by searching the Two Plus Two forum.
Huge database with Sit & Go's player results.
Sit and go strategy
Sit and Go Planet
Lots of advice focused on Sit & Go play.
Other poker games
Pai Gow Poker Advantage
Learn the strategy that gets you an advantage at pai gow poker