The data used in this blog can be found at the following websites, which provide exhaustive sources of NBA statistics:

Fivetimesfive Blog: 5 times 5 is an advanced NBA statistics blog. The authors are also involved in the development of new advanced basketball statistics/indexes, such as Involvement Rate or Direct Offensive Efficiency. Those advanced stats for individual NBA players are available on the New NBA Advanced Offensive Statistics webpage.

Stats NBA.com: NBA.com is the official site of the National Basketball Association. Stats.nba.com is their webpage devoted to NBA statistics data.

ESPN.com NBA Statistics: ESPN.com/NBA is an ESPN section devoted to the NBA basketball. In addition to NBA Statistics the section includes pages devoted to: scores, teams, schedules, standings, players, transactions, news wires, injures and columnists pages. Two of the products they are mostly known for are ESPN Insider and Hollinger Stats.

Basketball-Reference.com: Basketball-Reference.com provides statistics, scores, and history for the NBA, ABA, WNBA, and top European competition. It is a part of the Sports Reference sites, which cover other sports as well.

82games.com: 82games.com is geared towards providing innovative statistical coverage and analysis of the NBA for team executives, coaches, fans, and the media.
There are also other NBA statistics websites with advanced, innovative or fun ways of presenting NBA stats. Some of them are listed below:

FiveThirtyEight: FiveThirtyEight is a website that focuses on opinion poll analysis, politics, economics, and sports blogging. The website is also known for its NBA work, e.g. projecting the winner of each game and predicting each team’s chances of advancing to the playoffs and winning the NBA finals.

Nylon Calculus: The Nylon Calculus is a digital community dedicated to exploring basketball analytics through a mix of research, discussion, storytelling and education. Since the beginning of 2016/2017 season, Nylon Calculus has had a new home at FanSided.com.

StatMuse Blog: StatMuse is a sports Q&A website providing instant, visual answers to MLB, NBA and NFL questions. One of the editors is Justin Kubatko, also known for creating Basketball-Reference.com back in 2004.