In an earlier post, FretFriendly expressed some concern about the somewhat technical nature of some discussions that use sabermetric concepts, and other commenters on this post agreed. I'm not a moderator or anything here, nor am I an expert on sabermetrics, although I like to talk about it.
As I mentioned in a comment on FretFreindly's post, I would be sad if I thought that my tone or posts were making people feel like they can't talk baseball. That isn't my intent. I think it's something some of us need to work on corrrecting, but that's not what I'm posting about here. The thing is, a year ago, I wouldn't have known a lot of what I post about. It woud be fun to try to pose as an expert, but the truth is that just about anyone can learn this stuff with a bit of time (and no, it's not much more than you would spend googling Christina Hendricks or whatever her name is).
Again, I don't think being into this makes you any more or less of a baseball or Royals fan. But for those you are interested, here are just a few links to specific articles that I think are clear, reasonably short, and explain clearly stuff about player value. Best of all, almost all the information they reference is freely available. No, this isn't a comprehensive list, and isn't meant to be but it is a start.
Keep in mind that sabermetrics is a constantly developing field of research. I picked these articles because they are clear, short, and accessible. So this is a starting point, or at least something to give you an idea of what "WAR" or "Replacement level" or "FIP" mean. Different sabermetricians have different positions. Disagreement is how all human knowledge evolves, anyway.
Much or most of the stuff that Cameron writes, it must be said, derives from the ideas of Tom Tango and Mitchel Litchman. Their blog is for their Book, The Book. It's a great book, and a great blog, but I wouldn't start there, necessarily, but that is "the source" for so much of the "free" internet's sabermetrics, just so you know.
Some general informational links
wOBA - Weighted On-Base Average (The best offensive total value stat out there, for my money, for its accuracy, comprehensiveness, and ease of calculations. Easy to turn into runs created above/below average, too. Invented by Tom Tango)
The Joy of wOBA (Cameron's introduction)
Positional Adjustments (Cameron's explanation of Tangos' positional adjustments)
Evaluating Pitcher Talent (Dave Cameron. Explains the limitations of ERA)
Might I also humbly suggest my own Thoughts on Pitcher Value, which draws on the other stuff and goes through one kind of explanation of pitcher replacement level, sorts through ERA, RA, FIP, and tRA, and then uses examples from the Royals to show the differences. This is meant as an introductory reference peice. I do replacement level (using pitcher win%) a bit differently now, but the method there still works and is very easy.
The best publicly available "uberstats" for overall player value is found at FanGraphs, with their mostly Tango-derived Wins Above Replacement (WAR). Yes, it is better thanh anything at Baseball Prospectus (although that site is still very good for many things). I think that WAR sounds complicated, but is actually very straightforward one you realize that it is derivative of league average, and that it simply measures a players value with respect to average. Both of Cameron's series on these are very good introductions. I learned much of this from reading Tango, but Cameron's stuff is all in one place and is the same. For a Royals-specific example that draws on the same numbers, see my comment comparing Gordon and Guillen in 2008. You don't have to do it yourself, but once you understand the basic concept, I think it's very straighforward. These pieces are very short, so don't be intimidated
Cameron's FanGraphs Series on Win Values: Position Players
Part 1 (Introduction/Offense)
Part 2 (UZR/Fielding)
Part 3 (Positional Adjustments)
Part 4 (Replacement Level and Total values)
Part 5 (Total Values/Runs to Wins Conversions)
Part 6 (Converting Win Values to Dollar Values)
Pitcher Win Values
Part 1 (Introduction)
Part 2 (Using FIP instead of ERA)
Part 3 (Replacement Level for Pitchers)
Part 4 (Adjusting for Run Environment)
Part 5 (Adjusting for the Pitcher's effect on his own Run Environment)
Part 6 (Park Factors)
Part 7 (working through examples)
Bonus: For those who want to read something else from this site on the Royals in particular, see NYRoyal's How good is a #1, #2, #3, #4, #5 starting pitcher?
Fangraphs isn't the only good sabermetric site on the intertubez. The Hardball Times is also good. Colin Wyers (of Statspeak.net, more of a "hardcore" site, but very good) also recently did his own "total value" thing at THT, although it's a bit more involved.
That's more than enough for now. Feel free to ask questions -- I'm hardly an expert, but I (or one of the many people here who know more than I do) can try to answer. Remember, too (and this needs to be repeated) that this stuff is relatively recent, and is still in development. The point isn't to establish a new dogma, but to get more accurate through creating and refining how we think about baseball.
For me, the point it to enjoy it and think about it on another level. If you don't want to, you don't have to. But if you do want to, you could do worse than start with some of the links above.