The first thing you should do is read Dave's post at USSM, because it's a great overview of the current state of defensive analysis. Once you've done that, I urge you to go visit Baseball Musings (again), because David Pinto just published his individual shortstop PMR data for 2005, and it's good stuff. With UZR no longer available to the public, PMR is the best metric we have, so it's definitely worth your time to read about it and become familiar with the methodology.
Of course, all most people really care about are the results. And, at least for 2005, they aren't that surprising. Derek Jeter sucks. Yuniesky Betancourt is good. John McDonald could probably barehand a meteor and launch it back into solar orbit. What Pinto shows on his site are the number of outs each player made above or below what one could expect of him, given the batted balls he faced in the field. That's cool information to have.
It doesn't have to stop there, though. About a year ago, an Angels blogger worked on a way to convert PMR numbers into run figures, which is generally what people want to see more than anything when it comes to this stuff. You can read how he worked it out on his site - I'll spare you the calculations.
The last thing we need is a way to convert these run figures to above/below average, instead of above/below expected. Doing that only gives us a better idea of just how valuable a guy's defense really is relative to the rest of the league. For whatever reason, shortstops in 2005 turned only 96.1% of "expected" outs into "actual" outs, meaning that, if a given player performed exactly at his expected level, he'd still come out as being above-average. It's a little weird, and it might be a problem with the PMR model, but let's just assume that everything's okay for a second and look at some final numbers:
Yuniesky Betancourt: +16.7 runs above average per 150 games played
Wilson Valdez: +19.4
Mike Morse: -27.1
John McDonald: +54.0
Derek Jeter: -41.9 (Teehee)
Omar Infante: +28.6
I'm pretty skeptical that there could really be such a wide range between the best and the worst defensive shortstops in baseball, but that's what PMR is telling us was the case a year ago. Being but a single defensive metric, the standard caveats apply when it comes to working with these numbers, but if anything out there that's available for public consumption is going to give us a close approximation of how valuable certain players' defense really is, it's this. Besides, all I really wanted was some numerical evidence of Betancourt's awesomeness, and look, there it is! Neat.