As of September 5th, here are the best fielding teams in the league according to an average of STATS and BIS zone rating runs:

Anyone still wondering why the Yankees were so disappointing this year?  Or why Rangers' pitchers always seem to struggle?  That the Twins were so poor on defense makes their young rotation that much more impressive.  Milwaukee went from a bad fielding team to a good one in just one year.  You can credit moving Ryan Braun from 3B (-25 runs last year) to LF (+8 runs this year) for a lot of that improvement.  Ten of the top fifteen fielding teams are in the National League.

Here's a comparison of offensive runs above replacement, compared to average.  Sure, you could just order the teams by run scored, but that doesn't adjust for league or outs used:

I'm not sure anyone's shocked to see Boston and Texas near the top or San Francisco and Oakland at the bottom (it must be tough to be a fan of offense in the Bay Area these days).  The Rays are surprisingly high and the Angels surprisingly low.  And it will be a really impressive feat for the Diamondbacks to make the playoffs with a bottom five lineup

Lastly, at least on the team level, here are the teams with the best position players, offense and defense combined:

Wow, the Royals really just need to start over -- Tony Pena, Ross Gload, Jose Guillen, Mark Teahen, and Esteban German are a combined 53 runs worse than replacement level, and there are only five position players who accumulated more than one run above replacement level.

Going into 2008 the Cardinals' pitching staff was a big question mark, and they ended up letting the team down.  They had the best set of position players in the majors and still couldn't catch the Cubs or Brewers, who to be fair, were also both among the top eight teams.

How about the best and worst individual fielders at each position?

No, that Abreu number is not a typo.  The team on the left is about 250 runs better than the team on the right, just considering fielding alone.

And finally, here are the top 20 best and worst defensive players (fielding at position plus a position adjustment):

It's shocking how low Justin Morneau rates defensively this year.  Certainly some of it could weirdness in the batted ball distribution.

All stats courtesy of Justin.  I merely copied, pasted, pivot-tabled, and commented.