TerminologyI got a mail this morning asking what VORP and PECOTA are. That's a fair question. VORP stands for "Value over Replacement Player", which measures as objectively as possible the overall value of a player compared to a joe average bench player. Using a baseline of average bench players gives a good way to compare the overall value of a player across the season.
PECOTA is a projection system from the people at Baseball Prospectus. It's pretty complicated, but so far has done a better job than other projection systems.
A good glossary explaining modern baseball metrics (so called "sabremetrics") is available at Baseball Prospectus.