Statistics

Baseball Reference - Current and past statistics for every player, team and league throughout history.
http://www.baseball-reference.com/

FanGraphs - Major League and Minor League Baseball statistics presented in graphical format, with statistical analysis and projections of future performance
http://www.fangraphs.com

Baseball Statistics Nexus - Encyclopedia of baseball statistics, graphs, biographical information and commentary.
http://www.thebaseballnexus.com/

Pennant Race - Up to date graphs, charts and statistics for each team. Users can create unique custom comparison graphs.
http://www.pennant-race.com/

Major League Baseball - Player statistics from the official Major League Baseball web site.
http://mlb.mlb.com/stats/sortable_player_stats.jsp

MLB Home Run Paces - Career and current season home run pace statistics, updated daily.
http://www.hrpace.com

Last 30 - Graphs of hitting, pitching and fielding performance, presented as rolling averages for most recent 30 games.
http://www.last30.com/

Baseball Databank - Free source of annually updated files containing career and season information for players throughout Major League Baseball history.
http://www.baseball-databank.org/

HitTracker - Home run tracking and distance measurement, with comparisons allowing for wind, weather and altitude.
http://www.hittrackeronline.com/

Stats Baseball - Information as well as past and current statistics. Includes major award lists.
http://statsbaseball.homestead.com/

Graphical History of Baseball - Graphs for various historical statistics including lead leaders, fielding and attendance.
http://home.istar.ca/~mbein/baseball.html

Baseball Info Solutions - Commercial provider of baseball statistical information for teams, publications and online services.
http://www.baseballinfosolutions.com/

Excruciating Baseball Lists - Question and answer statistics in the form of trivia that include game scores and run streaks.
http://www.mikemav.com/xbl

Coolstandings - Presents baseball statistics and calculates the chance of each team making the playoffs.
http://www.coolstandings.com/playoff_standings2.asp?i=1

MadStatter.com - MLB Statistics - Team performance and scoring statistics presented in unique tabular formats.
http://www.madstatter.com/

Baseball Cube - Includes historical statistics, player profiles and related links.
http://www.thebaseballcube.com/

Retrosheet - Source of data files containing play-by-play accounts of most Major League Baseball games since 1956.
http://www.retrosheet.org/