Aside from the Dodgers, who are way out in front in the West, the Nationals (who are hands-down the worst team in baseball, and maybe the Padres and D-Backs; every NL team is basically in the same boat. They all have holes in their line-ups, voids in their pitching staff, and injuries they don't have the depth to replace. It's going to be a very interesting second half of the season. One hot streak can easily put a team in first in the NL East or Central and conversely a cold streak will put you in last. It's tough to predict what will happen because of this, but here is what I think.
NL East - The Mets are probably the best team, but they've been killed by injuries. The Phillies are leading right now, but their pitching is a mess, and it's hard to see a way for them to fix that. The most complete team right now is probably the Marlins. They have a porous defense, but their pitching and line-up are quite good. I think they'll make a run at it, but that the Mets will get just healthy enough to win the division with a pedestrian 88 wins.
NL Central - I went over this quite a bit yesterday, but I'll just re-iterate that I think the Cardinals can and should win this division. They have the best pitching staff, and the offense should warm up enough for them to pull away. The Brewers don't have the starting pitching, and the Cubs' line-up and bullpen is a mess. The Reds could be a surprise team though.
NL West - Obviously, it would be a huge shock for the Dodgers to falter here.
NL Wildcard - As I said before, basically 12 of the 16 teams in the NL are contenders for this. The biggest contenders are the Cubs, Phillies, Marlins, Giants and Rockies. All of these teams have major faults. The Giants have by far the best pitching, but desperately need a bat. If they can get that in a trade, I like their chances. If not, I'll take the experience and talent of the Phillies, but really it's a coin-flip between any of these clubs.
My predicted results would pit the Cards against the Giants in the first round. Not a match-up I would love with Lincecum and Cain maybe the best 1-2 punch in baseball. Carp-Waino is nothing to laugh at, but still. In other words, I'm kinda hoping the Giants DON'T get another bat, because they'd be a real tough out in the postseason.