Sabermetrics comes from the acronym for the Society for American Baseball Research, SABR. Sabermetrics is the statistical study of baseball; techniques of probability and statistics are used to discern real trends in baseball [for example, the qualities of hitters] from those that just seem to happen [for example, the quality of a player to "hit in the clutch"]. As such, sabermetrics is an oft-debated field of study.
Please feel free to submit any site that studies baseball from a statistical point of view.